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Issued  April  17,  1*09. 


HX64 102262 
UP171  .B43  The  influence  of  mus 

JEAfTE^U.  S.  DEPARTMENT   OF  AGRICULTURE. 

OFFICE  OF  EXPERIMENT  STATIONS— BULLETIN  208. 

C.    TRUE,    Director. 


THE  INFLUENCE  OF  MUSCULAR  AND  MENTAL 
WORK  ON  METABOLISM 


AND 


THE  EFFICIENCY  OF  THE  HUMAN  BODY 
AS  A  MACHINE. 


FRANCIS  G.  BENEDICT,  Ph.  D., 
Director  of  Nutrition  LaborahM'yof'pafnegie  Institution  of  Washington, 

AND 

THORNE  M.  CARPENTER,  B.  S., 
Chemist  of  Nutrition  Laboratory  of  Carnegie  Institution  of.  Washington. 


WASHINGTON: 
GOVERNMENT    PRINTING    OFFICE. 

1909. 


a?v\\ 


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1145  Issued  April  17, 1909. 

U.  S.  DEPARTMENT   OF  AGRICULTURE. 

OFFICE  OF  EXPERIMENT  STATIONS— BULLETIN  208. 

A.    C.   TRUE,    Director. 


THE  INFLUENCE  OF  MUSCULAR  AND  MENTAL 
WORK  ON  METABOLISM 


AM) 


THE  EFFICIENCY  OF  THE  HUMAN  BODY 
AS  A  MACHINE. 


BY 

FRANCIS  G.  BENEDICT,  Ph.  D., 
Director  of  Nutrition  Laboratory  of  Carnegie  Institution  of  Washington, 

AND 

THORNE  M.  CARPENTER,  B.  S., 
Chemist  of  Nutrition  Laboratory  of  Carnegie  Institution  of  Washington. 


WASHINGTON: 

GfOVEUNHENT    PRINTING    OFFICE. 

1  909. 


3^3 


OFFICE  OF  EXPERIMENT  STATIONS. 

NUTRITION  INVESTIGATIONS. 

A.  C.  True,  D.  Sc,  Director. 

E.  W.  Allen,  Ph.  D.,  Assistant  Director  and  Editor  of  Experiment  Station  Record. 

C.  F.  Langworthy,  Ph.  D.,  Expert  in  Nutrition. 

R.  D.  Milner,  Ph.  B.,  Assistant  in  Nutrition. 

(2) 


LETTER  OF  TRANSMITTAL 


U.  S.  Department  of  Agriculture, 

Office  of  Experiment  Stations, 

Washington,  D.  C,  January  4,  1909. 

Sir:  I  have  the  honor  to  transmit  herewith,  and  to  recommend  for 
publication  as  Bulletin  208  of  this  Office,  areportof  19  experiments  on 
the  effects  of  muscular  work  on  metabolism  and  the  efficiency  of  the 
human  body  as  a  machine,  and  44  experiments  on  the  effects  of 
mental  work  on  metabolism. 

These  investigations  were  carried  on  at  Wesleyan  University, 
Middletown,  Conn.,  in  cooperation  with  this  Department  by  F.  G. 
Benedict,  Ph.  D.,  who  was  then  professor  of  chemistry  at  Wesleyan 
University,  and  is  now  director  of  the  Nutrition  Laboratory  of  the 
Carnegie  Institution  of  Washington,  at  Boston,  Mass.,  and  T.  M. 
Carpenter,  B.  S.,  who  is  associated  with  Doctor  Benedict,  and  the 
work  forms  a  part  of  the  investigations  which  have  been  carried  on 
by  the  Department  for  the  purpose  of  studying  the  fundamental 
laws  of  nutrition  and  various  problems  which  depend  upon  them. 

The  results  which  were  obtained  furnish  accurate  and  interesting 
data  regarding  the  extent  of  the  effects  of  muscular  work  on  metab- 
olism but,  even  with  the  delicate  methods  followed,  do  not  indicate 
that  mental  work  affects  in  any  appreciable  way  the  indexes  of 
metabolism  which  were  studied. 

As  regards  the  effectiveness  of  the  body  as  a  machine,  experimental 
evidence  shows  that  body  efficiency  is  20  per  cent;  that  is,  for  every 
calorie  of  muscular  work  produced  by  the  body  a  total  of  5  calories 
of  energy  is  expended. 

Acknowledgment  should  be  made  of  the  service  rendered  in  these 
experiments  by  Mr.  X.  Butler,  a  professional  bicyclist,  who  volun- 
teered to  act  as  subject  of  experiments  on  muscular  work  and  body 
efficiency. 

The  courtesy  of  the  members  of  the  faculty  and  students  of 
Wesleyan  University  who  cooperated  in  the  experiments  on  the 
effects  of  menial  work  should  also  be  acknowledged. 

Respectfully, 

A.  C.  True, 

Director. 
I  [on.  James  Wilson, 

Secretary  of  Agriculture. 

(3) 


CONTENTS 


Page. 

Muscular  work  and  body  efficiency 9 

Introduction 9 

Relation  of  work  to  total  heat  output 10 

The  bicycle  ergometer -  -  -  -  11 

Construction • 11 

Principle  of  the  ergometer 13 

Method  of  calibrating  the  ergometer 14 

Results  of  ergometer  calibrations 1 G 

The  respiration  calorimeter 19 

Experiments  with  men 20 

Complete  metabolism  experiments 21 

Experiments  with  J.  C.  W 21 

Heat  production  during  rest 21 

Heat  production  duringwork 23 

Mechanical  efficiency 23 

Experiments  with  B.T.  D 24 

Experiments  with  A.  L.  L 25 

Work  of  coasting 27 

Twelve-hour  experiments  with  men 28 

Experiments  with  B.  F.  1).  and  E.  F.  S 28 

Experiment-  with  a  professional  bicyclist 29 

General  plan  of  the  experiments  and  the  results  obtained 29 

Influence  of  muscular  work  on  general  metabolism 31 

Water  vaporized 31 

Carbon  dioxid  excreted 32 

Oxygen  absorbed 33 

Conditions  inside  the  respiration  chamber 33 

General  discussion  of  results 34 

Personal  impressions  of  the  subjects  of  the  experiments 34 

Summary  of  results  of  muscular  work  experiments 34 

Mechanical  efficiency  of  the  human  body 36 

Methods  of  calculation  and  results 36 

"  i  toasting"  on  a  bicycle 38 

<  ialculation  of  mechanical  efficiency  based  on  coasting  on  a  bicycle.  38 

Internal  friction  of  le<^ 40 

Mechanical  efficiency  as  affected  by  varying  degrees  of  intensity 

I if  u'i  irk 41 

Comparison  of  results  with  computations  of  mechanical  efficiency  of 

six-day  bicycle  riders 43 

The  influence  of  mental  work  on  metabolism 45 

Earlier  investigations 45 

Measurements  of  mental  work 52 

Methods  of  measurii                if  menial  effort 53 

Chemical  transformations 54 

Measurement  of  heat 56 

General  plan  of  the  experiments 57 

Puke  rate 59 

ml  impressions 59 

Character  of  food  preceding  the  experiments 59 

Subjects  of  the  experiments ■ 59 

of  i lie  mental  work  experiments 60 

Method  of  calculation  of  body  weight  to  periods 60 


6 


The  influence  of  mental  work  on  metabolism — Continued. 
Statistics  of  the  mental  work  experiments — Continued. 

Mental  work  experiment  No.  1 

Mental  work  experiment  No.  2 

Mental  work  experiment  No.  3 

Mental  work  experiment  No.  4 

Mental  work  experiment  No.  5 

Mental  work  experiment  No.  6 

Mental  work  experiment  No.  7 

Mental  work  experiment  No.  8 

Mental  work  experiment  No.  9 

Mental  work  experiment  No.  10 

Mental  work  experiment  No.  11 

Mental  work  experiment  No.  12 

Mental  work  experiment  No.  13 

Mental  work  experiment  No.  14 

Mental  work  experiment  No.  15 

Mental  work  experiment  No.  16 

Mental  work  experiment  No.  17 

Mental  work  experiment  No.  18 

Mental  work  experiment  No.  19 

Mental  work  experiment  No.  20 

Mental  work  experiment  No.  21 

Mental  work  experiment  No.  22 , 

Summary  of  results  of  mental  work  experiments 

Control  experiments 

Statistics  of  the  control  experiments 

Control  experiment  No.  23 

Control  experiment  No.  24 

Control  experiment  No.  25 

Control  experiment  No.  26 

Control  experiment  No.  27 

Control  experiment  No.  28 

Control  experiment  No.  29 

Control  experiment  No.  30 

Control  experiment  No.  31 

Control  experiment  No.  32 

Control  experiment  No.  33 

Control  experiment  No.  34 

Control  experiment  No.  35 

Control  experiment  No.  36 

Control  experiment  No.  37 

Control  experiment  No.  38 

Control  experiment  No.  39 , 

Control  experiment  No.  40 

Control  experiment  No.  41 ■ 

Control  experiment  No.  42 

Control  experiment  No.  43 

Control  experiment  No.  44 

Summary  of  results  of  control  experiments 

Discussion  of  results  of  mental  work  and  control  experiments. 

Body  temperature 

Pulse  rate 

Water  vapor  excreted 

Carbon  dioxid  excreted 

Oxygen  absorbed 

Heat  production 

General  conclusions 


61 
62 
63 
64 
65 
65 
66 
67 
67 
68 
68 
69 
70 
70 
71 
72 
72 
73 
73 
74 
75 
75 
76 
78 
78 
78 
79 
80 
80 
81 
81 
82 
83 
83 
84 
84 
85 
86 
86 
87 
87 


89 
90 
90 
91 
91 
93 
93 
94 
95 
96 
97 
99 
100 


LUSTRATIONS. 


Page. 
Fig.  1.  The  bicycle  ergometcr 13 

2.  The  bicycle  ergometer  in  the  calorimeter  for  calibration 15 

3.  Curve  of  calibrations 18 

(7) 


INFLUENCE  OF  MUSCULAR  AND  MENTAL  WORK  ON  METABOLISM  AND 
EFFICIENCY  OF  THE  BODY  AS  A  MACHINE, 


MUSCULAR  WORK  AND  BODY  EFFICIENCY. 


INTRODUCTION. 

The  marked  and  immediate  influence  of  muscular  exertion  on  the 
transformations  of  matter  and  energy  in  the  body  has  long  served  as 
a  subject  for  experimentation.  The  earliest  experimenters  were 
enabled  to  make  observations  on  the  influence  of  severe  muscular 
exercise  on  the  body  functions  from  simple  observations  on  the  ap- 
pearance of  fatigue,  sensible  perspiration,  rapid  respiration  and  pulse 
rate,  and  loss  in  weight.  Such  superficial  observations  were  soon 
supplemented  by  others  more  or  less  accurate  regarding  the  amount 
of  work  that  the  body  could  do.  The  attempts  to  measure  this 
amount  of  work  have  been  numerous,  and  have  resulted  in  the  devel- 
opment of  several  sorts  of  apparatus  for  this  purpose. 

The  simplest  (and  perhaps  the  earliest)  device  for  measuring  work 
w  as  t  hat  of  lifting  a  weight  a  given  number  of  times.  From  the  well- 
known  relations  of  work  to  the  weight  times  the  height  to  which  it  is 
lifted,  it  was  possible  to  compute  in  foot-pounds  the  amount  of  work 
performed  by  a  man.  The  treadwheel,  which  is  described  by  Ilirna 
and  Chauveau,6  is  a  device  based  upon  the  same  physical  principle 
as  Lifting  a  weight.  The  subject  lifts  his  own  body  through  varying 
heights,  depending  upon  the  length  of  time  during  which  he  walks 
on  the  treadwheel  or  treadmill.  The  introduction  of  the  ergograph, 
which  has  been  elaborated  by  Mosso,0  enabled  studies  of  particular 
groups  of  small  muscles  to  be  made  with  great  accuracy.  Theergostal , 
which  has  been  introduced  in  recent  years,  particularly  by  dohann- 
Bond  and  Xunix,'  permits  the  bringing  into  play  of  the  powerful 
muscles  of  the  arm  and  back. 


Thermodynamique  et  I' Etude  du  Travail  chez  lea  &trea  vivants.     Pane,  L887 
bCompI  Rend.  Acad.  Sci.  [Paris],  L29(1899),  p.  249. 
cArch.  ttal.  Biol.,  L3i  L890),  p.  \s.\. 
*8kand.  Arch.  Physiol.,  II  (1901),  p.  273. 
'An!,.  I'll  ip.,p.  39. 

0) 


10 

In  recent  years  the  attempt  has  frequently  been  made  to  compute 
the  amount  of  work  performed  by  bicyclists  during  a  long  race.  In 
such  computations  the  chain,  tire,  and  the  resistance  of  the  bicycle 
are  taken  into  account. 

All  of  these  devices  for  determining  the  amount  of  work  done  are 
open  to  serious  error.  In  the  lifting  of  weights  there  is  a  large  amount 
of  extraneous  muscular  effort  which  must  be  very  inefficiently  applied 
to  the  weight.  Then  in  the  majority  of  the  experiments  in  which 
weights  were  lifted  the  same  subject  lowered  them,  and  the  work 
done  to  counteract  the  force  of  gravity  as  the  weight  was  lowered 
was  not  taken  into  consideration.  Of  the  ergographs,  that  of  Mosso 
has  been  the  most  used,  and  yet  the  work  of  lowering  the  weight  has 
not  been  duly  taken  into  consideration  in  this  form  of  instrument. 
The  ergograph  of  Halla  is  much  more  satisfactory  for  this  purpose, 
but  is  applied,  at  present  at  least,  only  to  small  groups  of  muscles. 
At  Yale  University  Prof.  Irving  Fisher6  has  used  Hall's  cushion 
ergograph  for  the  muscles  of  the  leg  and,  he  states,  with  great  success. 

The  chief  objection  to  the  principle  of  the  treadwheel  or  treadmill 
lies  in  the  fact  that  there  is  no  wholly  satisfactory  method  of  deter- 
mining the  work  of  forward  progression,  which  must  necessarily 
enter  into  the  estimate  of  the  work  done.  The  method  of  calculating 
the  work  performed  by  a  professional  bicyclist,  depending  upon  the 
resistance  of  the  chain,  tire,  and  air,  is,  we  believe,  most  unsatis- 
factory, as  was  brought  out  by  the  data  reported  by  Atwater,  Sher- 
man, and  Carpenter."  A  far  more  satisfactory  and  accurate  method 
is  that  employed  by  Berg,  Du  Bois-Iieymond,  and  Zuntz,d  in  which 
an  automobile  or  motor  cycle  was  used  to  tow  a  man  mounted  on  a 
regular  bicycle  around  a  track  at  different  rates  of  speed. 

The  ergostat,  relying  upon  the  muscles  of  the  arms,  must  of  neces- 
sity bring  into  play  a  large  number  of  other  muscles  which  are  ineffi- 
ciently applied  to  the  point  where  the  work  is  done. 

RELATION  OF  WORK  TO  TOTAL  HEAT  OUTPUT. 

Not  only  have  attempts  been  made  to  compute  the  total  energy  or 
work  done  by  man,  but  numerous  writers  have  likewise  attempted  to 
compute  the  ratio  between  the  amount  of  work  produced  and  the 
total  heat  output.  The  carbon  dioxid  output  was  used  as  early  as 
1844  by  Scharlinge  as  an  index  of  the  heat  production  and  oxidation 
processes  in  general.     Scharling's  method  of  performing  muscular 

a  Experimental  Physiology,  W.  S.  Hall,  1904,  p.  227. 
b  Private  communication. 

cU.  S.Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  98.     See  also  L.  Zuntz,  Unter- 
suchungen  iiber  den  Gaswechsel  und  Energieumsatz  des  Radfahrers.     Berlin,  1899. 
d  Arch.  Anat.  u.  Physiol.,  Physiol.  Abt.,  1904,  Sup.,  p.  20. 
e  Ann.  Chem.  u.  Pharm.,  45  (1843),  p.  214. 


11 

work  was  to  raise  and  lower  a  heavy  iron  bar.  During  this  process 
a  marked  increase"  in  the  output  of  carbon  dioxid  was  noted.  Zuntz 
and  his  associates  in  Germany,  and  Ohauveau  and  Tissot  in  France, 
have  determined  the  respiratory  epiotients  during  muscular  work. 
From  the  ratios  of  the  amounts  of  carbon  dioxid  and  oxygen  meas- 
ured during  rest  and  during  work  the  authors  have  attempted  to  com- 
pute not  only  the  amount  of  work  done  but  the  total  energy  eliminated. 

The  direct  measurement  of  the  heat  production  of  man  during 
muscular  work,  however,  has  been  made  possible  only  by  means  of 
the  respiration  calorimeter  at  Wesleyan  University,  Middletown, 
Conn.  This  apparatus  has  been  in  process  of  development  for  the 
last  twelve  years  in  connection  with  the  nutrition  investigations  of 
this  Department. 

During  one  of  the  early  experiments  with  this  apparatus  the  subject 
performed  a  considerable  amount  of  mechanical  work  by  raising  and 
lowering  a  weight,  and  on  those  days  during  which  the  work  was  per- 
formed there  was  a  marked  increase  in  the  output  of  carbon  dioxid 
oyer  the  resting  value.  Subsequently,  in  connection  with  further 
experiments  in  these  series,  an  improved  form  of  bicycle  ergometer 
was  devised  in  which  a  bicycle  was  so  adjusted  that  the  rear  wheel 
pressed  against  the  wheel  attached  to  the  armature  shaft  of  a  small 
dynamo.  From  the  amount  of  electricity  generated  the  amount  of 
external  muscular  work  performed  could  be  computed.  The  method 
of  calibrating  the  machine,  and  the  description  of  the  machine  itself, 
has  been  given  in  detail  in  an  earlier  bulletin  of  this  series,  in  an 
account  of  experiments  reported  by  Atwater  and  Benedict.0 

The  inequalities  of  the  surface  of  the  tire,  the  slip,  variations  in 
ten-ion  of  spring,  and  numerous  other  factors  rendered  the  limit  of 
error  on  this  machine  too  large  for  the  most  satisfactory  work,  and 
hence  a  special  form  of  bicycle  ergometer  was  constructed  in  which 
it  was  attempted  to  eliminate  in  so  far  as  possible  all  known  errors. 

The  apparatus  has  been  briefly  described  in  several  preceding  pub- 
lications,6 but  its  detailed  description,  method  of  calibration,  and  the 
reports  of  the  experiments  made  with  it  are  here  presented  in  detail 
for  the  firsl  time. 

THE  BICYCLE  ERGOMETER. 
CONSTRUCTION. 

Relying  on  the  powerful  leg  muscles  and  the  form  of  the  bicycle 
to   secure  the  greatest    efficiency  and   longest    continued   sustained 

effort,  the  ergometer  was  constructed  substantially   along    the   lines 

of  a  modern  bicycle.     The  rear  wheel  of  a  bicycle  was  replaced  by  a 

"  C  S.  Dept.  Agr.,  Office oi  Experiment  Stations  Bui    L36 

&  U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  17.',;  Yearbook  L904,  p.  205. 


12 

copper  disk  40.5  centimeters  in  diameter  and  6  millimeters  thick. 
This  disk  is  mounted  in  such  a  way  that  it  rotates  freely  on  a  ball- 
bearing axle.'  A  small  sprocket  wheel  is  attached  to  the  axle  and  is  in 
turn  connected  in  the  usual  manner  with  the  large  pedal  sprocket 
wheel  by  means  of  a  sprocket  chain.  A  wooden  frame  surrounds  the 
periphery  of  the  disk,  and  to  the  upper  part  of  the  frame  is  attached 
an  electro-magnet.  Binding  posts  are  attached  to  the  magnet  to 
connect  with  the  electric  cable  leading  to  the  observer's  table,  where 
the  strength  of  current  through  the  field  can  be  regulated  with  great 
accuracy.  The  field  of  the  magnet  is  so  extended  that  the  copper 
disk  rotates  in  the  center  of  the  field  with  but  a  very  small  air  gap 
between  the  surface  of  the  disk  and  the  surface  of  the  magnet,  and 
hence  the  resistance  is  wholly  that  of  magnetic  induction.  A  current 
of  1.25  amperes  induces  large  eddy  currents  in  the  copper  disk  to  such 
an  extent  that  the  resistance  is  very  noticeable,  and  as  the  speed  of 
the  rotating  disk  increases  it  becomes  very  much  heated.  In  the 
absence  of  a  commutator  the  currents  become  short-circuited  in  the 
disk  and  give  rise  to  the  generation  of  heat.  This  heat  is  radiated 
from  the  disk  into  the  surrounding  air. 

Obviously,  the  stronger  the  field  of  the  magnet  on  this  apparatus 
the  greater  are  the  currents  generated  in  the  disk  and  the  greater  is 
the  torque.  Variations  in  the  flux  density  of  the  field  are  obtained  by 
varying  the  strength  of  the  current  passing  through  the  coil.  By 
increasing  the  intensity  of  the  current  passing  through  the  electro- 
magnet any  desired  degree  of  resistance  can  be  obtained.  The  current 
is  supplied  from  a  storage  battery  of  seven  cells  in  series  with  a  milam- 
meter  and  adjustable  resistance,  and  the  current  is  kept  constant. 
The  resistance  of  the  field  coil  rises  with  a  rise  in  temperature  of  the 
coil,  so  that  it  is  necessary  to  adjust  the  series  resistance  at  the  start. 
The  resistance  of  the  field  coil  is  not  far  from  8  ohms.  In  general,  1.25 
amperes  are  passed  through  the  field,  as  this  has  been  found  to  produce 
the  most  satisfactory  torque  on  the  disk. 

To  anticipate  the  effects  of  long-continued  usage  especial  care  was 
taken  in  the  construction  of  the  ergometer,  and  after  four  years'  use 
the  apparatus  functionates  perfectly  and  shows  no  appreciable  deterio- 
ration or  variation  in  its  constants.  As  was  stated  above,  the  strength 
of  the  field  of  the  magnet  is  an  important  factor  in  determining  the 
amount  of  current  induced  in  the  disk.  This  depends  upon  several 
factors,  the  most  important  of  which  are  the  magnetic  conductivity 
of  the  core,  the  number  of  ampere  turns  around  the  core,  and  the 
width  of  the  air  gap.  The  core  and  poles  are  made  of  the  best  quality 
of  magnet  iron  obtainable  and  are  wound  with  No.  18  single-covered 
copper  magnet  wire.  The  general  construction  of  the  apparatus  can 
readily  be  seen  in  figure  1 . 

In  the  construction  of  the  apparatus  every  precaution  was  taken 
with  the  bearings,  selection  of  chain,  and  suspension  of  the  disk 


13 

to  secure  the  minimum  friction.  There  is  very  little  residual  mag- 
netism in  the  iron  cores,  and  hence  when  the  disk  is  rotated  and  no 
current  is  passed  into  the  magnet  the  wheel  rotates  freely  and  for 
several  minutes,  there  being  no  appreciable  resistance. 

Attached  to  the  frame  of  the  bicycle  is  a  spring  which  presses  con- 
tinually against  the  inside  of  the  large  sprocket.  As  the  sprocket 
turns,  a  disk  of  insulating  material  breaks  an  electric  circuit  for 
the  greater  part  of  the  time,  but  for  a  short  period  in  each  revolution 
the  spring  comes  in  contact  with  metal  and  completes  the  circuit, 
and  an  electric  current  from  four  dry  cells  actuates  an  automatic 
counter  on  the  observer's  table,   and  thus  each  revolution  of  the 


Fig.  i.    The  bicycle  ergometer. 


pedal  is  recorded.  As  pointed  out  above,  the  degree  of  resistance 
applied  to  the  rotating  disk  is  dependent  upon  the  current  passing 
through  the  electric  field.  A  large  uumber  of  tests  with  the  appa- 
ratus showed  that  a  current  of  1.25  amperes  caused  a  degree  of 
resistance  that  was  considered  to  be  hard  work  by  most  of  the  riders. 

PRINCIPLE  OF  THE  ERGOMETER. 

The  elect  tic   brake,  while  frequent  ly   Used   in   technical   machines,   is 

not  in  common  use  in  scientific  instruments.  For  a  thorough  under- 
standing  of   the   efficiency    of   tin-    apparatus    it    is    necessary    to   see 

clearly  that  there  is  no  friction  (in  the  common  acceptance  of  the 
term)  in  this  apparat  u  . 


14 

If  a  wire  is  passed  through  the  fields  of  an  electro-magnet,  a  differ- 
ence of  potential  will  be  present  at  the  ends  of  the  wire,  but  no  current 
will  flow  through  it,  and  no  energy  is  required  to  move  it  other  than 
that  necessary  to  overcome  gravity.  If,  however,  the  ends  of  the 
wire  are  connected  with  each  other,  a  current  will  flow  through  it 
and  additional  energy  will  be  required  to  move  it  through  the  mag- 
netic field.  This  energy  will  be  proportional  to  the  square  of  the 
strength  of  the  field  and  directly  proportional  to  the  speed. 

This  may  be  called  magnetic  friction,  and,  according  to  Lentz's 
law,  in  all  cases  of  magnetic  induction  the  induced  currents  have 
such  a  direction  that  their  reaction  tends  to  stop  the  motion  which 
produces  them.  If,  in  place  of  a  single-wire  conductor,  a  disk  is  so 
adjusted  that  it  can  be  rotated  between  the  poles  of  a  magnet,  the 
induced  currents  will  be  short-circuited  in  the  disk  as  soon  as  generated 
and  consequently  there  developed  into  heat.  Furthermore,  as  in 
the  case  of  the  wire,  the  induced  currents  will  tend  to  stop  the  motion 
of  the  rotating  disk,  and  thus  produce  an  effect  that  may  be  called 
that  of  an  electric  brake. 

METHOD  OF  CALIBRATING  THE  ERGOMETEE. 

The  primary  object  of  this  apparatus  is  to  measure  the  amount  of 
external  muscular  work  that  a  man  can  apply  to  the  pedals  of  a 
bicycle  ergometer.  The  ordinary  process  of  calibration  of  such  an 
apparatus  would  involve  the  use  of  some  form  of  cradle  dynamometer 
and  the  results  would  be  obtained  in  terms  of  foot-pounds,  which  in 
turn  would  be  converted  into  calories  or  British  thermal  units.  For 
the  purpose  of  studying  the  mechanical  efficiency  of  a  man,  it  is 
obviously  of  great  advantage  to  measure  the  external  muscular 
work  in  terms  of  calories.  During  his  early  development  of  this 
ergometer,  it  was  suggested  by  Prof.  W.  O.  Atwater  that  it  might 
advantageously  be  calibrated  by  placing  the  whole  apparatus  inside 
the  chamber  of  the  respiration  calorimeter  described  later. 

This  plan  was  adopted,  and  by  means  of  a  flexible  shaft  attached  to 
the  large  sprocket  the  apparatus  was  driven  by  electric  power  out- 
side the  chamber  at  different  rates  of  speed  from  50  to  85  revolutions 
per  minute.  A  current  of  1.25  amperes  was  then  passed  through 
the  electro-magnet  and  the  heat  evolved  measured  by  the  respiration 
calorimeter.  This  method  of  calibration  has  proved  eminently 
successful,  and  by  its  use  the  work  performed  is  measured  in  calories 
and  the  errors  incident  to  the  use  of  a  dynamometer  are  eliminated. 

The  method  of  installing  the  ergometer  in  the  respiration  chamber 
for  a  calibration  test  is  illustrated  in  figure  2. 

The  ergometer  is  placed  inside  of  the  chamber  in  a  vertical  position, 
with  a  shaft  from  the  large  sprocket  wheel  extending  through  the 
food  aperture,  and  by  outside  connections  by  pulley  and  belt  to  the 
main  shaft  it  can  be  rotated  at  any  given  speed.     A  current  is  passed 


15 

through  the  electro-magnet  and  the  whole  system  is  run  for  a  number 
of  hours,  the  heat  developed  being  measured  in  the  usual  way  by  the 
current  of  water  passing  through  the  calorimeter. 

In  the  calibration  of  the  ergometer,  about  two  hours  are  required 
for  the  calorimeter  and  the  heat-measuring  appliances  to  attain 
equilibrium.  At  the  end  of  that  time  the  heat  production  of  the 
ergometer  is  equal  to  the  heat  absorption  by  the  water  current  of  the 


l  i'..  2.  -The  bicycle  ergometer  in  the  calorimeter  for  calibration. 

calorimeter  and  the  experiment  proper  can  be  started.  Asa  vu\v, 
these  tests  lasl  from  four  to  six  hours  after  equilibrium  is  obtained. 
'I'hc  calibrations  have  been  extremely  satisfactory  and  the  ergom- 
eter give;,  .i  very  accurate  measure  of  external  muscular  work  done 
by  the    ubjecl  v.  hen  operal  ing  ii . 

"  A    the  friction  of  the  machine  was  considered  to  be  extre ly  low, 

a  test  was  made  to  measure  this  in  calories.     Ii  wasfoundthal  when 
running  the  apparatus  with  uo  current  through  the  electro-magnet, 


16 


due  precautions  being  taken  to  prevent  conduction  of  heat  out  of  the 
calorimeter  through  the  flexible  shaft7  each  revolution  corresponded 
to  a  heat  production  of  0.001547  calorie,  which  is  a  direct  measure  of 
the  friction. 

This  value  includes  any  effect  of  the  slight  residual  magnetism  in 
the  field. 

As  the  result  of  a  number  of  experiments,  it  was  found  that  each 
revolution  of  the  large  sprocket  wheel,  when  a  current  of  1.25  amperes 
was  passing  through  the  electro-magnet,  resulted  in  a  heat  production 
of  0.0231  calorie.  It  is  obvious,  therefore,  that  to  compute  the 
external  muscular  work  of  a  subject  riding  this  ergometer  it  is  only- 
necessary  to  know  the  number  of  revolutions  of  the  pedal,  obtained 
from  the  electric  counter,  and  in  case  the  current  through  the  fields 
is  1.25  amperes  to  multiply  by  the  factor  0.0231. 

RESULTS  OF  ERGOMETER  CALIBRATIONS. 

Since  the  ergometer  was  constructed  a  number  of  calibrations  have 
been  made  according  to  the  method  described  in  the  preceding  sec- 
tion. The  results  of  these  calibrations  have  been  recorded  chrono- 
logically in  the  following  table : 

Heat  produced  in  ergometer  calibrations. 


(o) 

(6) 

(c) 

(d) 

(«) 

(/) 

(g) 

(h) 

(0 

(?) 

Date. 

Duration 

of 

period. 

Heat 
meas- 
ured. 

Cor- 
rected 

to  C20. 

Change 
of 
calo- 
rim- 
eter. 

Change 
of  tem- 
pera- 
ture of 
absorb- 
ers. 

Heat  of 

mag- 
netiza- 
tion. 

Heat 
pro- 
duced. 

Num- 
ber of 
revolu- 
tions. 

Heat 
per 
revolu- 
tion. 

Cur- 
rent. 

Num- 
ber of 
revo- 
lutions 
per 
min- 
ute. 

1903. 

h. 

771. 

s. 

Calories 

Calories 

Calories 

Calories 

Calorics 

Calories 

Calorics 

Amp. 

Oct.      5 

6 

17 

6 

772. 39 

774.24 

-3.6 

+0.60 

-68..74 

702.  50 

29, 967 

0. 0234 

1.250 

79 

6 

6 

52 

46 

741. 22 

743. 15 

-9.0 

+  .29   -53.42 

681. 02 

30, 006 

.0227 

1.250 

102 

9 

6 

50 

34 

854.62 

856. 84 

-2.4 

-  .98 

-74.74 

778. 72 

33,554 

.0232 

1.250 

82 

12 

4 

9 

30 

532.  90 

534.23 

-   .88 

-52.88 

480. 47 

20,837 

.0231 

1.250 

72 

12 

4 

20 

30 

635. 07 

636. 72 

+  1.07 

-47.41 

590. 38 

25,833 

.0229 

1.250 

99 

1904. 

Oct.    26 

7 
5 

10 
39 

50 
30 

873. 05 
642.43 

874. 45 
643. 71 

-78.59 
-61.99 

795.86 
585.  29 

34,158 
25,214 

.0233 
.0232 

1.250 
1.250 

79 

Nov.  18 

+3.0 

+  .57 

74 

18 

5 

14, 

27 

664.13 

665. 78 

+2.4 

+  1.05 

-57.25 

611. 98 

25,964 

.0236 

1.250 

83 

1905. 

May   13 

6 

30 

0 

480. 40 

481. 17 

+3.0 

-27.60 

456.  57 

27,769 

.0164 

.800 

71 

15 

6 

0 

0 

360.54 

361.01 

+  .6 

-1.93 

-19.40 

340. 28 

27,361 

.0124 

.700 

76 

16 

6 

0 

0 

501.  07 

502. 02 

+  -6 

+  1.58 

-32.46 

471. 74 

26,713 

.0176 

.900 

74 

17 

6 

0 

0 

725. 30 

726. 90 

+  .6 

-  .82 

-65.64 

661. 04 

29,157 

.0227 

1.250 

81 

18 

6 

0 

0 

381. 76 

382.52 

-1.19 

-19.40 

361.  93 

27,290 

.0133 

.700 

76 

19 

6 

0 

0 

438.28 

439. 20 

-  .6 

+  .99 

-25.48 

414. 11 

26,532 

.0156 

.800 

74 

20 

6 

0 

0 

743. 32 

745. 10 

+   .6 

+  1.21 

-65.64 

681. 27 

29,958 

.0227 

1.250 

83 

22 

2 

21 

0 

199. 70 

200. 16 

-7.2 

+  .31 

-12.71 

180.  56 

10,654 

.0170 

.900 

76 

23 

7 

0 

0 

520. 81 

521. 85 

+  2.4 

-  .80 

-29.72 

493.  73 

31,586 

.0156 

.800 

75 

24 

7 

0 

0 

611.  56 

612.  91 

+  1.42 

-37.87 

576. 46 

32,950 

.0175 

.900 

78 

26 

4 

0 

0 

250. 74 

251. 19 

+  1.29 

- 12.  94 

239.54 

19,227 

.0125 

.700 

80 

27 

7 

0 

0 

836. 02 

838. 03 

-4.2 

-  .62 

-76.58 

756. 63 

32,945 

.0230 

1.250 

78 

29 

6 

0 

0 

395. 30 

396. 09 

+  -6 

-1.25 

-19.40 

376.04 

28,899 

.0130 

.700 

80 

29 

6 

0 

0 

671. 14 

672. 82 

-  .6 

-1.52 

-50.46 

620. 24 

30,035 

.0207 

1.100 

83 

The  table  shows  the  date  of  each  experiment,  the  period,  the  heat 
measured  (expressed  in  calories),  and  the  corrections  necessary  to  de- 
termine the  exact  amount  of  heat  resulting  from  the  rotation  of  the 


17 


ergometer.  Thus  the  heat  as  measured  by  the  calorimeter  must  be 
corrected  to  the  standard  calorie  used  in  all  experiments  thus  far  made 
with  this  respiration  calorimeter,  i.  e.,  the  amount  of  heat  required  to 
raise  1  kilogram  of  water  from  19.5°  to  20.5°.  This  is  commonly  ex- 
pressed as  the  calorie  at  20°  or  C20. 

Even  with  the  most  accurate  manipulation  on  the  part  of  the  phys- 
ical assistants,  it  is  difficult  to  have  an  experiment  so  conducted  that 
the  temperature  of  the  chamber  is  the  same  both  at  the  beginning  and 
at  the  end  of  the  experiment.  Consequently,  slight  corrections  are 
necessary  for  the  capacity  of  the  calorimeter  to  store  or  yield  heat. 

The  he  at -absorbing  system  consists  of  a  copper  pipe,  to  which  a  large 
number  of  disks  are  soldered,  to  increase  the  heat-absorbing  surface. 
At  the  beginning  of  the  experiment  the  temperature  of  this  system 
may  be  roughly  assumed  to  be  the  average  temperature  of  the  ingoing 
and  outcoming  water.  At  the  end  of  the  experiment  the  average  tem- 
perature of  tins  system  may  be  somewhat  different,  and  hence  a  cor- 
rection is  necessary  for  the  heat  capacity  of  the  absorbers. 

Finally,  in  this  form  of  bicycle  ergometer  it  is  necessary  to  introduce 
an  electric  current  to  magnetize  the  field  of  the  apparatus,  and  this 
current  passing  through  a  resistance  in  the  calorimeter  generates  a 
small  amount  of  heat.  From  the  strength  of  the  current  and  the  re- 
sistance the  heat  developed  may  be  very  accurately  computed.  This 
is  recorded  in  column  e  of  the  table  under  the  head  of  "heat  of  mag- 
netization." 

The  actual  amount  of  heat  produced  by  the  ergometer  is  given  un- 
der the  head  of  "heat  produced." 

The  number  of  revolutions  of  the  pedals  was  registered  by  the 
electric  counter  previously  described  and  also  by  a  mechanical  coun- 
ter. In  each  experiment  the  total  number  of  revolutions  is  recorded. 
In  column  h  the  heat  per  revolution  obtained  by  dividing  the  total 
heat  production  by  the  total  number  of  revolutions  is  recorded. 

The  strength  of  current  used  to  magnetize  the  field  and  the  number 
of  revolutions  per  minute  are  recorded  in  the  last  two  columns  of  the 
table. 

The  results  of  the  calibrations  given  in  the  previous  table  are  ex- 
pressed  chronologically.  The.  average  results  for  the  different 
strengths  of  curreni  through  the  field  .-ire  given  in  the  following  table: 

Average  heat  production  of  ergometer  for  currents  of  different  strength. 


'.'Ill  of 

con 

Beat  per 
revolution 

of  ergom- 
eter, 

ngth  of 
current. 

1  [eat  per 
revolution 
of  ergom- 
eter. 

Am/nr'. 
(1700 

.800 

.!XXI 

CalorU 

II.  OIL'S 

.oifie 

.0174 

i.  mo 
1.260 

Calorie. 

ii.  0207 

.0281 

r0076     Hull.  20 


18 

In  the  majority  of  the  experiments  reported  beyond,  this  latter 
value  is  used,  i.  e.,  that  every  revolution  of  the  pedal,  when  the  field 
of  the  ergometer  is  carrying  a  current  of  1.25  amperes,  results  in  the 
production  of  0.0231  calorie  of  heat.  An  inspection  of  the  results 
given  in  the  table  (p.  16)  shows  that  the  results  for  the  magnetization 
at  1.25  amperes  ranged  from  0.0227  to  0.0236. 

The  results  are  on  the  whole  extremely  satisfactory,  and  we  believe 
that  the  factors  thus  determined  are  well  within  the  limit  of  error  of 
physiological  experimenting.  The  calibrations  have  been  expressed 
in  the  form  of  a  curve  (fig.  3) . 

This  curve  shows  that  the  heat  per  revolution  is  almost  directly 
proportional  to  the  strength  of  the  current.  The  curve  shows  a  suffi- 
cient number  of  established  points  to  serve  for  the  computation  of  the 


CURVE    OF    CALIBRATIONS. 

1.3- 

1.  1    - 

1.0  - 
.9 
.8 
.  7 

-      .7 

. 

TI20       .0/30     .0/40       .0150       -0/60      .0/70      .0180      .0130     .0200     .02/0      .0220    -0&. 

?o 

HEAT     PER    REVOLUTION. 

Fig.  3. — Curve  of  calibrations. 

heat  production  with  any  strength  of  current  through  the  field.  For 
the  lower  currents,  especially  between  0.700  and  0.800  ampere,  other 
points  should  be  found. 

An  inspection  of  the  figures  in  the  table  (p.  16)  shows  that,  as  might 
be  expected  from  Lentz's  law,  with  a  given  resistance,  the  amounts 
of  heat  developed  are  directly  proportional  to  the  number  of  revolu- 
tions of  the  pedals  and  independent  of  the  rate  of  speed.  Thus  in  the 
test  of  October  12,  from  11.20  a.  m.  to  4.10  p.  m.,  with  72  revolutions 
per  minute,  the  heat  per  revolution  was  0.0231  calorie,  while  during 
the  second  part  of  the  test,  from  6.07  p.  m.  to  10.27  p.  m.,  with  99 
revolutions  per  minute,  the  heat  per  revolution  was  0.0229  calorie,  a 
discrepancy  well  within  the  limit  of  error  when  the  small  amounts  of 
heat  measured  are  taken  into  consideration.  It  is  obvious,  therefore, 
that  this  form  of  apparatus  is  especially  well  designed  for  studying 
the  heat  production  during  the  mechanical  motion  of  riding  a  bicycle, 


19 

for  while  the  majority  of  bicyclists  are  capable  of  maintaining  a 
fairly  constant  rate  of  speed,  this  apparatus  is  so  constructed  that 
any  irregularities  in  speed  are  wholly  without  influence  on  the  cor- 
rectness of  the  final  results.  In  order,  therefore,  to  compute  the  total 
energy  of  external  muscular  work,  it  is  only  necessary  to  multiply 
the  number  of  revolutions  by  the  factor  for  the  degree  of  intensity 
through  the  field.  In  by  far  the  larger  number  of  experiments  the 
subjects  rode  the  ergometer  when  the  current  was  1.25  amperes. 

A  number  of  subjects  have  ridden  the  bicycle  ergometer  inside  of 
the  respiration  chamber  for  four  periods  of  two  hours  each  with  this 
degree  of  resistance  at  a  rate  of  about  60  to  70  revolutions  per  minute 
with  no  degree  of  discomfort.  Indeed,  in  certain  experiments  the 
subjects  have  ridden  for  twelve  to  fourteen  hours  out  of  the'  twenty- 
four.  On  the  other  hand,  this  degree,  of  resistance  is  undoubtedly 
somewhat  more  than  that  of  riding  along  a  level  road.  While  most 
riders  have  preferred  a  resistance  corresponding  to  1.25  amperes 
through  the  field,  the  strength  of  current  has  been  varied  in  different 
experiments  from  0.7  to  1.25  amperes. 

After  a  few  moments'  riding  the  disk  becomes  very  warm,  but  soon 
the  generation  of  heat  is  exactly  equaled  by  the  loss  of  radiation  and 
i he  temperature  increase  ceases.  Obviously,  at  the  end  of  an  experi- 
ment the  disk  is  warm  and  loses  considerable  heat  on  cooling. 

THE  RESPIRATION  CALORIMETER. 

The  particular  form  of  respiration  calorimeter  used  in  these  experi- 
ments has  been  described  in  detail  in  a  number  of  places.0 

It  will  suffice  here  to  state  that  the  apparatus  is  a  so-called  "closed- 
circuit  "  respiration  apparatus  permitting  the  direct  determination  of 
the  carbon  dioxid  and  water  vapor  elimination  and  the  oxygen  con- 
sumption. The  experimental  periods  may  be  made  as  short  as  two 
hours,  as  was  the  case  in  many  of  the  experiments  here  reported. 

As  a  calorimeter  the  apparatus  is  so  constructed  that  the  larger 
portion  of  the  heal  eliminated  is  absorbed  by  a  current  of  cold  water 
passing  through  cooling  pipes  or  heat  absorbers  inside  the  chamber. 
The  amount  of  water  ami  the  temperature  through  which  it  is  warmed 
in  it-  passage  through  the  chamber  are  accurately  measured.  By 
special  devices  the  double  walls  are  rendered  adiabatic,  and  hence  the 
apparatus  has  no  "cooling  correction."  The  heal  required  to  vapor- 
ize water  inside  the  chamber  is  also  taken  into  consideration  in  the 
final  computations. 

Tests  <»f  the  apparatus  in  which  known  amounts  of  ethyl  alcohol 
have  been  burned  inside  the  chamber  show  that  the  apparatus  meas- 
ures with  considerable  accuracy  1  he  four  important  factors  of  general 
metabolism,  namely,  carbon  dioxid  and  water  vapor  output,  oxygeu 
absorpl ion.  and  beal  eliminal ion. 

i     -    Depl    Agr.,  Office  of  Experiment  Stations  Bui.  175;  I     S.  Dept.  Agr.,  year- 
book 1904,  j.  205;  (  arnegie  [net.  Washington  Pub.  42. 


20 

EXPERIMENTS  WITH  MEN. 

In  the  construction  of  the  bicycle  ergometer  care  was  taken  to  see 
that  the  adjustment  of  the  pedals,  seat,  and  handle  bars  was  such 
that  they  could  be  adjusted  to  suit  almost  any  rider.  Having  dem- 
onstrated that  it  was  comfortable  to  ride  and  substantially  con- 
structed, a  number  of  experiments  were  made  on  men  riding  the  ergom- 
eter inside  of  the  respiration  calorimeter  chamber.  Some  of  these 
experiments  have  already  been  published  and  indeed  in  considerable 
detail  by  Benedict  and  Milner.a  They  were  primarily  designed  to 
study  the  relative  efficiency  of  the  fats  and  carbohydrates  as  a  diet 
for  muscular  work,  an  amplification  of  earlier  work  with  a  less  perfect 
form  of  ergometer. 

In  the  study  of  the  different  diets  the  measurements  with  the  ergom- 
eter formed  an  integral  part  of  the  experiment.  But  at  that  time 
the  chief  object  was  to  insure  that  the  subjects  performed  identically 
the  same  amount  of  external  muscular  work  on  all  the  days  of  the 
experiment.  While  it  was  desirable  to  know  exactly  the  external 
muscular  work  performed  for  the  purpose  of  comparing  the  two 
diets,  the  constancy  of  the  amount  performed  each  day  rather  than 
the  absolute  amount  was  of  the  greatest  importance. 

In  that  publication  no  especial  discussion  of  the  mechanical  work 
performed  or  the  efficiency  of  man  as  a  machine  was  included,  since 
it  was  deemed  more  advisable  to  discuss  these  problems  along  with 
some  subsequent  experiments  made  primarily  with  the  view  of  study- 
ing the  relationship  between  the  energy  of  external  muscular  work 
and  the  total  heat  output. 

A  few  experiments  were  made  in  which  the  subject  remained  inside 
the  respiration  chamber  but  twelve  hours,  i.  e.,  the  day  period.  The 
total  metabolism  as  indicated  by  the  carbon  dioxid  and  water  vapor 
output,  oxygen  intake,  and  heat  elimination  was  studied  for  this 
period.  Comparing  the  total  heat  production  during  this  twelve- 
hour  period  with  the  heat  production  during  the  same  period  when 
the  subject  was  at  rest  enabled  a  comparison  to  be  made  between 
the  energy  of  external  muscular  work  and  the  total  heat  production. 
It  was  thus  possible  to  measure  the  heat  required  for  external  mus- 
cular work  without  including  the  variations  in  heat  production  during 
periods  when  work  was  not  performed. 

Finally  a  series  of  experiments  was  made  with  a  professional 
bicyclist,  who  performed  an  excessive  amount  of  work  on  the  ergom- 
eter during  periods  of  from  two  to  four  hours.  The  resting  metabo- 
lism of  this  same  subject  was  also  determined  and  hence  a  satisfactory 
basis  for  comparison  was  available. 

a  U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  175. 


21 

COMPLETE  METABOLISM  EXPERIMENTS. 

As  stated  above,  these  experiments  were  a  continuation  of  a  series 
of  experiments  instituted  in  this  laboratory  to  study  the  relative 
efficiency  of  fats  and  carbohydrates  in  diets  for  muscular  work.  They 
continued  from  one  to  six  or  more  days,  and  included  complete  bal- 
ances of  matter  and  energy. 

The  experiments  were  made  with  three  young  men,  students  or 
former  students  in  Wesleyan  University,  J.  C.  W.,  B.  F.  D.,  and 
A.  L.  L. 

EXPERIMENTS  WITH  J.  C.  W. 

The  subject  was  a  powerful  college  athlete,  a  university  track  man, 
and  possessed  great  endurance.  During  one  day  he  rode  sixteen 
hours  with  no  special  discomfort  or  after  effects.  He  had  been  identi- 
fied with  a  number  of  earlier  experiments  with  the  respiration  calo- 
rimeter, a  but  in  these  earlier  experiments  the  muscular  work  was 
unsatisfactorily  measured  with  the  form  of  bicycle  dynamo  ergometer 
then  in  use. 

In  these  experiments  the  attempt  was  made  to  duplicate  an  earlier 
series  in  which  the  diet  containing  a  large  proportion  of  fat  was  com- 
pared with  the  diet  containing  a  large  proportion  of  carbohydrates, 
on  days  when  substantially  the  same  amount  of  external  muscular 
work  was  performed. 

The  first  experiment  in  which  this  subject  used  the  new  ergometer 
w ras  met  abolism  experiment  No.  56.  For  four  days  before  this  experi- 
ment began  he  partook  of  substantially  the  same  diet  that  was  eaten 
during  the  experiment  proper.  Although  in  this  preliminary  period 
he  was  not  inside  the  respiration  chamber,  he  nevertheless  rode  the 
bicycle  ergometer  for  the  same  number  of  hours  he  proposed  to  ride 
while  in  the  chamber.  During  this  period  the  diet  contained  a  large 
proportion  of  fat.  The  metabolism  experiment  proper  continued  for 
three  days  inside  the  respiration  chamber,  and  the  subject  partook  of 
a  fat  diel  throughout  the  period.  During  this  experiment  the  total 
output  of  carbon  dioxid,  water  vapor  and  heat,  and  the  intake  of  oxy- 
gen were  carefully  determined.     The  nitrogen  balance  was  also  found. 

A  second  experiment  made  with  this  same  subject  was  a  duplicate 
of  the  first,  save  thai  the  diet  consisted  for  the  most  part  of  carbo- 
hydrates. There  was  a  four-day  preliminary  period  and  also  a  three- 
experimenl  in  the  chamber. 

HEAT    PRODUCTION    DURING    REST. 

In  order  to  compare  the  resting  metabolism  with  that  during  work, 
a  four-day  resl  experiment  with  this  subject  had  been  made  some 
time  before.     It  is  much  to  be  regretted  thai  a  resl  experiment  did 

«  U.S.  Depl    \/i  ,  Office  of  Experiment  Stations  Bui.  L36. 


22 

not  immediately  precede  or  follow  the  work  experiments,  for  the  one 
rest  experiment  with  food  (No.  35)  with  this  subject  was  made  over 
two  years  before.  Since,  however,  in  this  study  the  primary  object 
was  a  comparison  of  the  fats  and  carbohydrates,  the  importance  of 
a  repetition  of  the  rest  experiment  was  not  at  that  time  appreciated, 
and  the  pressure  of  other  work  prevented  the  securing  of  these  most 
important  and  valuable  data. 

The  heat  production  obtained  in  several  rest  experiments  with 
J.  C.  W.  is  given  in  the  table  herewith.  While  the  resting  metabolism 
of  this  subject  was  carefully  studied  in  experiment  No.  35,  for  pur- 
poses of  comparison  similar  data  for  four  other  experiments  covering 
five  days  are  appended.  During  these  experiments  the  subject  con- 
sumed no  food. 

Heat  -production  in  rest  experiments  with  J,  C.  W. 


Experiment. 

Date. 

7  a.  m. 

to 
1  p.  m. 

1  p.  m. 

to 
7  p.  m. 

Total 

12 
hours. 

7  p.  m. 

to 
1  a.  m. 

1  a.  m. 

to 
7  a.  m. 

Total 

12 
hours. 

Total 

24 
hours. 

With  food. 
No.  35 

Dec.  9-10, 1900  .... 
Dec.  10-11,1900... 
Dec.  11-12,1900... 
Dec.  12-13,1900... 

Calo- 
ries. 
703 
657 
644 
663 

Calo- 
ries. 
680 
671 
676 
665 

Calo- 
ries. 
1,383 
1,328 
1,320 
1,328 

Calo- 
ries. 
625 
595 
644 
568 

Calo- 
ries. 
406 
464 
449 
479 

Calo- 
ries. 
1,031 
1,059 
1,093 
1,047 

Calo- 
ries. 
2,414 

2,387 
2,413 
2,375 

667 

673 

1,340 

608 

449 

1,057 

2,397 

Dec.  13-14, 1900  . . . 
Jan.  19-20, 1901  ... 
Mar.  6-7, 1901 
Apr.  1-2, 1902 
Apr.  2-3, 1902 

Fasting. 
No.  36 

627 
551 
492 
597 

084 

611 
517 
488 
599 
600 

1,238 
1,068 
980 
1,196 
1,284 

557 
498 
509 
681 
607 

458 
461 
457 
485 
457 

1,015 

959 

966 

1,166 

1,064 

2,253 

No.  39 

2,027 

No.  42 

1,946 

No.  51.... 

2,362 

2,348 

All  fasting  experi- 
ments,   average 

590 

563 

1, 153 

570 

464 

1,034 

■2, 187 

In  the  table  the  results  are  given  for  the  periods  from  7  a.  m.  to 
1  p.  m.,  1  p.  m.  to  7  p.  m.,  7  p.  m.  to  1  a.  m.,  and  1  a.  m.  to  7  a.  m. 

For  purposes  of  comparison  the  total  for  each  twelve-hour  period  is 
also  shown.  The  total  heat  production  for  the  twenty-four  hours  is 
given  in  the  last  column.  The  results  show  that  on  the  whole  there  was 
a  somewhat  lower  heat  production  during  fasting  than  during  periods 
with  food.  Without  attempting  to  go  into  any  specific  discussion  of 
the  metabolism  during  fasting  and  with  food,  it  may  here  be  said 
that  on  all  fasting  days  the  subject  undoubtedly  lived  under  condi- 
tions of  much  less  muscular  activity  than  during  days  when  food 
was  consumed. 

Since  on  the  work  days  the  work  was  all  performed  during  the 
periods  from  7  a.  m.  to  7  p.  m.,  we  have  to  do  here,  then,  only  with  the 
resting  metabolism  for  these  periods.  It  was  found  that  the  average 
heat  production  on  four  days  of  rest,  from  7  a.  m.  to  7  p.  m.,  was 


23 

1,340  calories,  while  during  inanition  the  heat  production  was  1,153 
calories.  In  the  subsequent  discussion  and  comparison  of  the  rest 
with  the  work  periods  1,340  calories  will  be  used  as  a  basis. 

HEAT    PRODUCTION    DURING    WORK. 

The  following  table  gives  the  total  heat  production  of  this  subject 
for  the  six  days  of  the  work  experiments.  The  results  are  recorded 
only  for  the  period  from  7  a.  m.  to  7  p.  m.,  when  the  total  work  was 
done. 

I!, at  equivalent  of  muscular  work  and  corrected  amount  of  heat  produced  (J.  C.    W.), 

7  a.  in.  to  7  p.  in. 


Experiment. 


Work. 


No.  56. 

No.  57. 


Date. 


Apr.  27-28. 1903 
Apr.  28  29,  I'.h i.: 
Apr.  29-30,1903 
Mav  7-8, 1903. . 
May  8-9, 1903.. 
Mav  9-10,  L903. 


(o) 
Heat 
equiva- 
lent  of 

muscular 
work. 


Calories. 
569 
601 
538 
657 
563 
587 


(b) 

(c) 

Heat  pro- 

Heat pro- 
duced. 

duced 
over  rest- 

ing me- 

tabolism. 

Calorics. 

Calories. 

a  3, 959 

2,019 

a  4, 139 

2,799 

a  3, 834 

2,494 

4,309 

2,969 

4,056 

2,716 

•1. 131 

2,791 

Effi- 
ciencv 
(ax  100) 


Per  cent. 
21.7 
21.5 
21.  6 
22.1 
20.  7 
21.0 


a  Heat  eliminated  (corrected  for  30  calories  from  bed  and  bedding). 

The  heat  equivalent  of  the  muscular  work  performed  on  the  bicycle 
ergometer,  obtained  by  multiplying  the  number  of  revolutions  by 
0.0231 .  is  recorded  in  column  a.  The  results  obtained  show  that  the 
external  muscular  work  performed  varied  from  day  to  day.  It 
averaged  about  580  calories  for  the  six  days  of  the  two  experiments. 

The  heat  production  from  7  a.  m.  to  7  p.  m.  is  recorded  in  column 
b.  For  the  first  three  days,  i.  e.,  experiment  No.  56,  it  was  impossible, 
owing  to  insufficient  data,  to  compute  the  heat  production.  Amounts 
recorded  show  the  heat  elimination,  corrected  for  the  estimated 
amount  of  heat  stored  in  the  bed  clothing  and  given  off  during  the 
first  period  of  the  day,  i.  e.,  30  calories.0 

MECHANICAL    EFFICIENCY. 

As  stated  above,  ihe  resting  metabolism  of  this  subject  was  found 
to  be  1,340  calories  during  the  period  from  7  a.  m.  to  7  p.  m.  On 
the  first  day  of  experiment  No.  56,  therefore,  this  subject  produced 
1,340  2,619  calorie-  of  heat  ill  performing  569  calories  of 
external  muscular  work.  Thus  the  body  was  able  to  transform  21.7 
per  cent  of  the  total  energy  above  the  resting  metabolism  into  external 
muscular  work.     A  similar  computation  for  the  remaining  days  of 


l"  pi    '. gr    Office  of  Experiment  Stations  Bui.  136,  j>.  157. 


24 

the  work  experiments  with  this  subject  shows  that  with  the  varia- 
tions in  the  heat  of  muscular  work  there  were  corresponding  varia- 
tions in  the  total  energy  above  the  resting  metabolism,  but  the 
excess  energy  transformed  into  external  muscular  work  was  about 
21.5  per  cent  for  each  day  of  the  experiments. 

EXPERIMENTS  WITH  B.  F.  D. 

One  experiment  in  which  the  bicycle  ergometer  was  used  was 
made  with  this  subject.  It  continued  for  only  one  day  and  was 
preceded  by  a  three-day  rest  experiment.  Thus  the  experiment 
may  be  taken  as  an  indication  of  the  influence  of  lack  of  training  on 
muscular  efficiency. 

The  data  showing  the  heat  production  of  this  subject  are  given  in 
the  table  below,  together  with  corresponding  data  for  two  rest 
experiments,  during  one  of  which  the  subject  fasted. 

Heat   equivalent  of  muscular  work  and  corrected  amount  of  heat  produced  (B.  F.  D.), 

7  a.  m.  to  7  p.  m. 


Experiment. 

Date. 

(a) 
Heat 
equivalent 
of  muscu- 
lar work. 

(6) 

Heat 
produced. 

(c) 
Heat  pro- 
duced over 
resting  me- 
tabolism. 

(d) 

Efficiency 
(oX100)H-r. 

Work. 
No.  61    . 

Jan.  30-31, 1904 

Calories. 
419 

Calories, 
a  3, 421 

1,185 
1,237 
1,309 

Calories. 
2,177 

Per  cent. 
19.2 

Rest  with  food. 
No.  60 

Jan.  27-28, 1904 

Jan  28-29  1904                          

Jan.  29-30, 1904 

1,244 

Dec.  18-19, 1903 

Rest  fasting. 
No.  59    . 

1,181 
1,134 
1,130 

Dec.  19-20, 1903 

Dec.  20-21,1903...              

a  Heat  eliminated  (corrected  for  30  calories  from  bed  and  bedding). 

The  average  amount  of  heat  produced  daily  during  the  rest  experi- 
ment with  food  was  1,244  calories,  while  for  the  fasting  experiment 
the  corresponding  amount  was  1,148  calories.  The  latter  experiment 
is  not  used  for  comparison  with  a  work  experiment,  however,  since 
the  work  was  performed  under  conditions  similar  to  those  of  the 
food  experiment. 

During  the  work  period  from  7  a.  m.  to  7  p.  m.,  B.  F.  D.  produced 
3,421  calories  of  heat,  while  during  the  rest  experiment  he  had  pro- 
duced on  the  average  1,244  calories.  The  difference,  2,177  calories, 
'is  the  amount  of  heat  produced  in  performing  an  amount  of  external 
muscular  work  corresponding  to  419  calories  of  energy.  The  external 
muscular  work,  therefore,  constituted  19.2  per  cent  of  the  energy 
produced  in  excess  of  that  required  by  the  subject  when  at  rest. 


25 

EXPERIMENTS  WITH  A.  L.  L. 

The  subject  A.  L.  L..  a  student  in  Wesleyan  University,  entered 
the  respiration  calorimeter  for  a  series  of  experiments  which  covered 
thirteen  days.  The  first  seven  days  were  work  experiments  (Xos.  62, 
63.  and  04).  of  which  the  last  was  with  severe  muscular  work.  On  the 
eighth  day  (experiment  Xo.  65)  the  subject  rested,  sleeping  the  greater 
part  of  the  time.  On  the  ninth  day  (experiment  Xo.  66)  he  prepared 
the  ergometer  for  riding,  dressed  and  undressed,  mounted  and  dis- 
mounted, but  did  no  riding.  On  the  tenth  and  eleventh  days 
(experiment  Xo.  67)  he  rode  the  ergometer  the  usual  number  of 
revolutions  but  without  any  resistance.  On  the  twelfth  and  thir- 
teenth days  he  fasted.  The  full  details  of  the  fasting  experiments 
have  been  reported  elsewhere,"  and  have  been  cited  in  a  report  of 
experiments  with  J.  C.  W.  and  B.  F.  D.  in  an  earlier  bulletin  b  of  this 
series. 

Subsequently  a  four-day  fasting  experiment  with  this  man  was 
made,  and  the  results  of  the  resting  metabolism  both  during  the  one- 
day  experiment  (experiment  Xo.  65)  with  food  and  the  six  fasting 
days  are  included  in  the  table,  page  26.  It  is  somewhat  unfortunate 
that  during  experiment  Xo.  65  the  subject  slept  the  greater  part  of 
the  day  to  recuperate  from  the  severe  work  of  the  da}*  before. 

On  the  next  day,  experiment  Xo.  66,  the  muscular  activity  was 
unquestionably  greater  than  during  the  previous  day,  since  eight 
times  during  the  da}'  the  subject  prepared  the  ergometer  for  mount- 
ing and  removed  a  portion  of  his  clothes. 

It  is  evident  from  the  above  statement  that  neither  experiment 
Xo.  65  nor  66  was  abnormal  rest  experiment."  Under  the  circum- 
stances it  seemed  best  to  average  the  heat  production  for  the  two 
days  and  assume  that  the  result  represents  the  heat  production  of 
this  subject  under  conditions  of  "normal  rest"  with  food,  or  under 
conditions  similar  to  those  obtained  in  the  rest  experiment  with 
J.  C.  W. 

In  experiment  No.  04  the  subject  rode  eleven  hours  and  the  day's 
work  was  accompanied  by  an  enormous  heal  production.  The  work 
was  continued  until  after  .'!  o'clock  in  the  morning,  and  the  heat  pro- 
duction from  7  a.  m.  April  22  to  4  a.  m.  April  23  was  6,843  calories, 
of  which  057  were  measured  as  external  muscular  work  on  the 
ergometer.  The  total  heat  production  on  this  day  is  worthy  of  note, 
Bince  from  7  a.  m.  April  22  until  7  a.  m.  April  23  the  subject  produced 
7,1  13  calories  <<\'  heat.  The  results  of  this  series  of  experiments  with 
A.  L.  L.,  together  with  the  heat   produced  during  fasting,  is  recorded 

in  t  tie  accompanying  table. 

arnegje  In-: .Washington  Pub.  77. 
'-I'.  B.  Dept.  AgrM  Office  of  Experiment  Stations  Bui.  17"). 


26 


Heat  equivalent  of  muscular  work  and  corrected  amount  of  heat  produced  (A.  L. 

7  a.  m.  to  7  p.  m. 


L.) 


Experiment. 


Work. 


No.  62. 
No.  63. 
No.  64. 


Rest  with  food. 


No.  65. 
No.  66. 


Average  of  Nos.  65  and  66. 


Coasting. 


No.  67. 


Restfasling. 


No.  68. 
No.  69. 


Date. 


Apr.  16-17,  1904. 
Apr.  17-18,  1904. 
Apr.  18-19,  1904. 
Apr.  19-20,  1904. 
Apr.  20-21,  1904. 
Apr.  21-22,  1904. 
Apr.  22-23,  1904. 


Apr.  23-24,  1904  . 
Apr.  24-25,  1904  . 


Apr.  25-26,  1904. 
Apr.  26-27,  1904. 

Apr.  27-28,  1904. 
Apr.  28-29,  1904. 
Dec.  16-17,  1904. 
Dec.  17-18,  1904. 
Dec.  18-19,  1904. 
Dec.  19-20,  1904. 


(a) 
Heat  equiv- 
alent of 
muscular 
work. 


Calories. 
459 
458 
460 
460 
460 
458 
6  957 


(6) 

Heat  pro- 
duced. 


Calorics. 

a  3, 599 

a  3, 578 

3,602 

3,657 

3, 573 

3,518 

c  6, 843 


1,203 
1,351 


1,277 


1,585 
1, 669 

1,178 
1,183 
1,026 
1,175 
1,121 
1, 055 


(c) 

Heat  pro- 
duced over 
resting  me- 
tabolism. 


Calories. 
2,322 
2,301 
2,  325 
2,380 
2,296 
2,241 
4,638 


(d) 

Efficiency 
(aXlOOKc. 


Per  cent. 
19.8 
19.9 
19.8 
19.3 
20.0 
20.4 
20.6 


a  Heat  eliminated,  corrected  for  30  calories  from  bed  and  bedding. 

b  8.01  a.  m.  to  3.01  a.  m. 

c  Heat  eliminated,  7  a.  m.  to  4  a.  m. 

The  method  -of  computing  the  proportion  of  energy  transformed 
into  external  muscular  work  in  experiments  Nos.  62  and  63  is  exactly 
the  same  as  that  explained  on  page  23.  The  heat  equivalent  of 
muscular  work  was  almost  the  same  for  each  day,  i.  e.,  458  to  460 
calories.  The  heat  produced  during  these  days  varied  from  3,518 
to  3,657  calories,  and  the  heat  required  over  and  above  the  resting 
metabolism  (1,277  calories,  the  average  of  experiments  Nos.  65  and 
66)  was  not  far  from  2,300  calories.  The  lowest  was  2,241  calories 
on  April  21-22;  the  highest,  2,380  calories,  on  April  19-20.  The 
average  percentage  of  efficiency  was  remarkably  constant,  for  al- 
though there  was  considerable  difference  between  the  first  and  third 
days  of  experiment  No.  63,  the  average  for  the  three  days  was  very 
similar  to  the  average  for  the  three  days  of  experiment  No.  62. 

Of  especial  interest  is  the  percentage  efficiency  in  the  severe  work 
experiment  No.  64.  On  the  whole  this  subject  transformed  about 
19.9  per  cent  of  the  excess  heat  into  external  muscular  work. 

For  deducting  the  heat  production  of  resting  metabolism  for  the 
severe  work  experiment,  the  heat  production  during  the  period  from 
7  a.  m.  to  4  a.  m.  of  experiment  No.  65  was  used.  This  was  found  to 
be  2,205  calories.  Deducting  this  from  the  total  heat  production  of 
experiment  No.  64,  6,843  calories,  leaves  4,638  calories  as  the  heat 
production  necessary  to  produce  mechanical  work  the  heat  equiva- 
lent of  which  is  957  calories. 


27 

WORK   OF   COASTING. 

In  this  experiment  the  subject  rode  the  ergometer  without  elec- 
trical resistance  for  two  days,  the  number  of  revolutions  on  both 
days  being  the  same  as  during  experiments  Nos.  62  and  63.  Theo- 
retically, at  least,  the  values  for  the  two  days  of  experiment  No.  67 
should  be  the  same.  On  the  first  day  of  the  experiment,  however, 
there  were  1,5S5  calories  of  heat  produced  from  7  a.  m.  to  7  p.  m., 
and  on  the  second  day  nearly  90  calories  more,  i.  e.,  1,669  calories. 
Deducting  the  value  for  resting  metabolism  from  these  two  values 
shows  that  in  order  to  overcome  the  friction  of  the  machine  and  the 
internal  friction  of  the  legs,  the  subject  transformed  308  and  392 
calories,  respectively. 

A  measure  of  the  friction  of  the  ergometer  without  eledtrical  resist- 
ance has  shown  that  every  revolution  of  the  pedals  results  in  the  pro- 
duction of  0.001547  calorie.  When  the  electrical  brake  is  used  with 
a  current  of  1.25  amperes  the  amount  of  heat  produced  per  revolution 
of  the  ergometer  is  0.023 1  calorie.  Assuming  that  the  friction  remains 
constant,  about  6.5  per  cent  of  the  total  heat  resulting  from  one  revo- 
lution of  the  pedals  is  due  to  friction.  Accordingly,  if  sufficient 
external  muscular  work  is  done  to  produce  460  calories  of  heat,  29.9 
calories  will  be  produced  as  the  result  of  friction.  Under  the  above 
conditions,  therefore,  a  rider  whose  mechanical  efficiency  is  20  per 
cent  will  expend  149.5  calories  to  overcome  the  friction  of  the  ergom- 
eter. Deducting  this  amount  from  the  total  heat  output  above 
the  resting  value  gives  158.5  calories  and  242.5  calories  as  the  energy 
required  to  overcome  the  friction  of  the  muscles.  Owing  to  unavoid- 
able circumstances,  in  these  experiments  the  agreement  between  the 
results  for  the  two  days  is  very  unsatisfactory  and  the  computations 
are  probably  open  to  considerable  error. 

It  may  reasonably  be  contended  that  another  method  of  measuring 
the  mechanical  efficiency  of  the  man  could  be  more  correctly  obtained 
by  deducting  the  total  heat  production  during  the  coasting  experi- 
ment from  that  during  work  and  using  the  difference  to  compute  the 
total  heal  of  external  muscular  work.  Thus  if  we  take  the  average 
of  the  two  days  of  experiment  No.  67,  the  heat  production  for  the 
period  from  7  a.  m.  to  7  p.  in.  was  1,627  calories,  but  during  this 
period  there  was  produced  by  the  friction  of  the  ergometer  29.9 
calories.  The  average  heal  equivalent  of  muscular  work  of  the  six 
days  of  experiments  Nos.  62  and  63  was  459  calories,  the  total  heat 
produced  3,588  calories,  and  deducting  from  the  total  produced 
1  .'127,  which  is  the  heal  produced  during  the  coasting  period,  we  have 
1,961  calories  as  the  heal  above  the  rest-coasting  metabolism.  If  is 
necessary,  however,  also  to  deduct  29.9  calories  from  the  heal  equiva- 
lent  of  muscular  work,  and  thus  it,  is  seen  thai  (lie  1,961  calories 
eliminated  above  the  energy  of  coasting  metabolism  resulted  in  the 
production  of  129.1  calories  of  external  muscular  work.     Of  this  1,961 

c;dorie>  21.9  pel'  cent    WQ&  eonverled   into  external  mUSCUlaT  work. 


28 


TWELVE-HOUR  EXPERIMENTS  WITH  MEN. 
EXPERIMENTS  WITH  B.  F.  D.  AND  E.  F.   S. 

The  next  series  of  experiments  with  the  bicycle  ergometer  was 
conducted  with  B.  F.  IX,  who  had  been  the  subject  of  an  earlier 
experiment.  In  this  series  of  experiments  the  subject  entered  the 
respiration  chamber  early  in  the  morning  and  remained  quiet  until 
7  a.  m.  During  the  first  day  he  rode  the  ergometer  a  total  of  25,959 
revolutions.  The  subject  worked  in  four  two-hour  periods,  although 
the  heat  measurements  were  made  in  three-hour  periods.  No 
attempt  was  made  to  have  the  work  uniform  throughout  all  periods. 
On  the  second  day,  March  2,  the  experiment  did  not  continue  after 
1  p.  m.  On  the  third  day  the  resting  metabolism  of  the  subject  was 
determined  for  purposes  of  comparison.  The  average  number  of 
revolutions  per  minute  was  60  on  the  first  day  and  56  on  the  second, 
there  being  a  little  less  than  half  as  much  work  done  on  the  second 
day. 

With  the  subject  E.  F.  S.,  the  number  of  revolutions  on  the  one 
day  of  the  experiment,  i.  e.,  March  5,  was  somewhat  greater  than  on 
the  first  day  with  B.  F.  D.  The  rate  of  revolution  varied  from  56 
to  63  per  minute.  In  all  the  short  experiments  with  these  two  men 
the  current  through  the  magnet  had  a  strength  of  1.25  amperes. 
The  results  are  collected  for  purposes  of  comparison  in  the  following 

table : 

Heat  produced  in  experiments  with  B.  F.  D.  and  E.  F.  S. 


Date. 

Period. 

(a) 

Heat 
produced. 

(&) 
Num- 
ber of 
revolu- 
tions. 

(0 

Number 

ofrevolu- 

tions  per 

minute. 

(d) 
Current. 

(«) 

Heat 
equiva- 
lent of 
muscular 
work. 

(/) 
Heat 
produced 
over  rest- 
ing me- 
tabolism. 

(9) 
Effi- 
ciency 
(fXlOO) 
+/■ 

B.  F.  D. 

Work. 

March  1, 1904. 
March  2, 1904. 

Rest  with  food. 

March  3,  1904. 

7  a.m.  to  7  p.m.. 
7  a.  m.  to  1p.m.. 

7  a.  m.  to  7  p.  m.. 
7  a.  m.  to  1  p.  m.. 

7  a.  m.  to  7  p.m.. 

Calories. 
4, 085.  44 
1, 962.  80 

1, 338.  64 
682.  83 

25, 959 
12, 645 

60 
56 

Amperes. 
1.250 
1.250 

Calories. 
599. 65 
292. 10 

Calories. 
2, 746. 80 
1, 279. 97 

Per  cent. 
21.83 
22.82 

E.  P.  S. 
Work. 

March  5, 1904. 

4, 782.  02 

26, 495 

61 

1. 250 

612.  03 

o3, 382. 02 

IS.  10 

a.  Resting  metabolism  assumed  as  1,400  calories.     See  page  29. 

For  obtaining  the  resting  metabolism  with  B.  F.  D.  the  values  found 
on  March  3  were  used  instead  of  those  in  the  earlier  experiments.  For 
the  six  hours  on  March  2  the  corresponding  six  hours  on  March  3 
were  taken  as  indicating  the  resting  metabolism. 

No  resting  experiment  with  E.  F.  S.  was  made,  as  the  subject  left 
Middletown  shortly  after  the  conclusion  of  this  experiment.  His 
body  weight  was  80  kilograms,  and  from  a  large  amount  of  data 


29 

obtained  with  other  subjects,  it  is  highly  probable  that  his  resting 
metabolism  would  be  not  far  from  1,400  calories  for  the  period  from 
7  a.  m.  to  7  p.  m.  Accordingly  in  the  computations  given  in  the  table 
this  resting  metabolism  has  been  assumed. 

EXPERIMENTS  WITH  A  PROFESSIONAL  BICYCLIST. 

Since  it  was  believed  that  experiments  with  a  subject  who  had  long 
been  trained  for  bicycle  riding  would  give  most  interesting  result- 
regarding  the  efficiency  of  man  as  a  machine,  and  that  with  such  a 
subject  the  most  satisfactory  results  with  this  form  of  ergometer 
could  be  obtained,  arrangements  were  made  with  a  professional 
bicyclist  to  come  to  Middletown  and  spend  a  number  of  days  riding 
the  ergometer  inside  the  respiration  chamber.  He  was  so  much 
interested  in  the  outcome  of  the  experiments  that  he  volunteered  to 
act  as  subject  and  in  every  way  seconded  our  efforts  to  secure  accurate 
and  complete  experiments,  and  his  intelligent  appreciation  of  the 
scientific  nature  of  the  work  contributed  in  large  measure  to  the 
success  of  the  experiments.  The  experiments  were  made  from 
October  21  to  24,  1904,  and  from  January  23  to  26,  1905. 

The  subject  X.  B.  was  35  years  of  age,  weighed  66  kilograms, 
and  was  172  centimeters  in  height.  Since  early  life  he  had  been 
engaged  in  bicycle  riding  and  had  established  himself  as  one  of  the 
foremost  professional  bicycle  riders  in  America.  His  experience  had 
included  not  only  short  races  but  also  the  more  tiring  and  strain- 
producing  six-day  bicycle  races.  In  excellent  condition,  practically 
a  total  abstainer  from  alcoholic  beverages,  he  was  an  ideal  subject 
for  the  experiments. 

GENERAL  PLAN  OF  THE  EXPERIMENTS  AND  THE  RESULTS 

OBTAINED. 

The  experiments  with  X.  B.  were  all  short  experiments  and  he  did 
not  remain  in  the  calorimeter  over  night.  In  general  the  subject 
entered  the  respiration  chamber  about  one  hour  before  the  actual 
experimental  period  began.  In  the  work  experiments,  as  soon  as  he 
entered  the  calorimeter,  he  began  to  ride  the  ergometer,  and  alter 
the  calorimeter  had  readied  temperature  equilibrium  the  experiment 
proper  was  begun.  Thus  the  temperature  conditions  inside  the 
chamber  were  approximately  the  same  at  the  beginning  and  at  the 
Slid  of  each  experiment.  The  periods  usually  lasted  from  one  and 
one-half  to  three  hours,  and  inmost  experiments  duplicate  periods 
could  he  obtained  and  the  accuracy  of  the  measurements  was  thus 
cheeked  to  ;i  certain  extent . 

The  first  experiment,  which  was  made  October  21,  1904,  began  at 
at  _'.:$!t.:;o  in  the  afternoon,  and  continued  lor  approximately  two 
hours.  During  this  period  the  subject  rode  the  ergometer  with  a 
current  of  1.25  amperes,  and  the  total  metabolism  as  measured  d\ 
the  carbon  dioxid  output,  oxygen  intake,  and  heal  elimination  was 


30 


obtained.  On  the  following  morning  a  three-hour  rest  experiment 
was  made  to  secure  the  resting  metabolism  of  the  subject.  At  the 
conclusion  of  this  rest  experiment  the  subject  did  not  leave  the  res- 
piration chamber,  but  after  a  rest  of  one  hour,  during  which  he  ate 
his  lunch,  began  to  ride  the  ergometer,  and  a  work  experiment  was 
begun  at  2  p.  m.  which  lasted  three  hours.  The  strength  of  current 
and  the  number  of  revolutions  per  minute  were  substantially  the  same 
as  in  the  experiment  of  the  previous  day.  On  October  24  a  three- 
hour  experiment  was  made  in  which  the  subject  rode  the  ergom- 
eter without  resistance.  This  experiment  was  therefore  a  so-called 
"coasting"   experiment. 

Three  months  later  a  more  extended  series  of  experiments  was 
made  with  this  subject.  On  January  23,  1905,  a  two-hour  rest  ex- 
periment was  followed  by  two  one  and  one-half  hour  periods  of  work, 
during  which  the  current  of  1.25  amperes  was  passed  through  the  mag- 
net of  the  ergometer. 

Later  the  degree  of  resistance  applied  to  the  ergometer  was  ad- 
justed to  correspond  as  nearly  as  Mr.  Butler  could  estimate  with 
the  amounfof  work  per  hour  done  during  a  six-day  race,  since  experi- 
ence showed  that  the  current  of  1.25  amperes  was  somewhat  too 
strong,  and  consequently  three  experiments  were  made  with  the 
strength  of  the  current  0.9,  0.8,  and  0.7  ampere,  respectively.  On 
January  24  the  subject  rode  for  two  two-hour  periods  against  a  re- 
sistance of  0.9  ampere,  and  on  the  following  day  he  rode  for  two  two- 
hour  periods  with  less  resistance  (0.8  ampere). 

On  January  26  two  experiments  were  made.  During  the  first  the 
subject  "coasted"  and  during  the  second  he  rode  the  ergometer 
against  a  resistance  of  0.7  ampere.  The  actual  records  of  the  ex- 
periments are  shown  in  the  following  table: 

Heat  produced,  carbon  dioxid  eliminated,  oxygen  absorbed,  and  water  vaporized  in  experi- 
ments with  N.  B. 


Date. 

Period. 

Current. 

Heat  pro- 
duced. 

Heat 
equiva- 
lent of 
work 
done. 

Num- 
ber of 
revo- 
lu- 
tions. 

Num- 
ber of 
revo- 
lu- 
tions 
per 
min- 
ute. 

Carbon 
dioxid 
elim- 
inated. 

Oxy- 
gen ab- 
sorbed. 

Water 
vapo- 
rized. 

1904. 
Oct.    21 
22 

2.40  p.  m.  to  4.25  p.  m... 
9.20  a.  m.  to  12.24  p.m.. 

2  p.  m.  to  4.58  p.  m 

9.10  a.m.  to  12.10  p.m... 

10.59  a.  m.  to  12.59  p.  m. . 
2.16p.m.  to 3.46 p.m.... 

3.46  p.  m.  to  5.17  p.  m 

9.47  a.  m.  to  11.45  a.  m. . . 
11.45a.  m.  to  1.47 p.  m. .. 
11.03  a.  m.  to  1.02  p.m... 

1.02  p.m.  to  3.02  p.  m 

10.36a.  m.  to  12.36 p.m.. 
12.36p.m.  to 2.36 p.m... 

A  mperes. 
1.250 
Rest. 
1.250 

Coasting. 

Rest. 
1. 250 
1.250 
.900 
.900 
.800 
.800 
Coasting. 
.700 

Calories. 
1, 101.  31 

290.80 
1, 827.  93 

547. 35 

179. 30 
914. 35 
952. 61 
934. 11 
948. 77 
779.90 
819. 23 
363. 19 
764.  72 

Calories. 
184. 06 

7,968 

76 

Grains. 
379. 07 
87.83 
617.  74 
186. 45 

58.81 
347.  44 
320.  21 
302.  86 
323.  46 
248. 20 
279.  52 
127. 00 
276. 38 

Grams. 

45.53 

275. 79 
265.  97 
281.77 
284. 16 
227.  95 
251. 41 
114.85 
222. 14 

Grams. 
149. 73 
145. 86 

22 
24 

343. 54 

14, 872 
14,874 

84 
83 

226. 78 
167. 77 

1905. 
Jan.    23 

63.85 

23 
23 
24 
24 
25 
25 
26 

171. 06 
174. 64 
157.  49 
157.  47 
127. 56 
133. 27 

7,405 
7,560 
9,051 
9,050 
8,177 
8,543 
9,919 
9,361 

82 
83 
77 
74 
69 
71 
83 
78 

103. 61 
102. 65 
109.30 
147. 85 
136.  92 
101.74 
101. 19 

26 

119. 82 

110. 72 

31 

Since  the  length  of  the  experiments  varied  somewhat,  the  results 
have  all  been  computed  to  amounts  per  hour,  and  these  values  are 
given  in  the  table  herewith: 

Results  oft  vperiments  with  N.  B.  calculated  to  one-hour  basis. 


Date. 

Period. 

(a) 

Current. 

(6) 

Water 
vapo- 
rized. 

(c) 
Carbon 
dioxid 

elimi- 
nated. 

Oxygen 
absorbed. 

• 
(«) 

Heat  pro- 
duced. 

Heat 
equiva- 
lent of 
work 
done. 

(g) 
Beat 
above 
resting 
metabo- 
lism. 

(h) 

Effi- 
ciency 

(/xiooH?. 

1904. 

Oct.    ill 

First... 

First . . . 

First . . . 

First . . . 
Second. 
Third.. 

First . . . 
Second. 

First . . . 
Second. 
First . . . 
Second. 

Amperes. 

1 .  25 
Rest. 

1.  25 

Coasting. 

1  25 
1.25 
.90 

.(HI 

.80 

.80 

Coasting. 

.70 

85. 1 12 
47.  43 
76.  39 
55.92 

31.93 
68.  89 

67  43 
55.  38 
72.96 

68  84 
50.87 
50.  60 
55.36 

Grama. 

215  24 

28.  56 

208.07 

62.  15 

29.41 
231  03 
210  36 
153  45 
159  62 
L24.79 
139  76 

63.  50 
138.19 

Grams. 

( hlorii   . 
625. 35 
94.17 
616. 16 
182. 45 

89.65 
607  99 
625.80 
4"3  30 
468. 21 
392   13 
409  62 
181.  60 
382.36 

Calories. 
104. 51 

Calorics. 
531. 18 

Per  cent. 
19.68 

•>•> 

1 15.71 

521.99 

22.17 

24 

1905. 
Jan.   23 

22.  77 
183  38 
1_4.   2 
142.  ~7 
140  23 
114.  til 
125.  71 

57  43 
111.07 

23 
23 
24 
24 

25 
25 
26 

113.75 
114.73 
79  80 
77  71 
64.  14 
66.  64 

518.34 
536.  15 
383.  65 
3"8.  56 
302.48 
319. 97 

21.95 
21.40 
20.  .SO 
20.  53 

21.29 

20.83 

26 

59.91 

292.71 

20.  47 

In  the  January  scries  of  experiments  it  was  possible  to  secure  an 
approximate  measurement  of  the  amount  of  oxygen  absorbed,  and  in 
the  table  are  included  the  amount  of  carbon  dioxid  eliminated,  water 
vaporized,  oxygen  absorbed,  and  the  heat  production. 

INFLUENCE  OF  MUSCULAR  WORK  ON  GENERAL  METABOLISM. 

The  value-  recorded  in  the  table  above  showing  the  amount  of  water 
vaporized,  carbon  dioxid  eliminated,  and  oxygen  consumed  indicate 
the  marked  influence  of  muscular  activity  on  the  general  metabolism. 

Of  especial  importance  in  this  discussion  are  the  heat  production  and 
the  heat  equivalent  of  work  done.  As  a  result  of  the  intense  muscular 
work  performed  by  this  subject  the  heat  production  reached  the  astound- 
ing maximum  of  626  calories  per  hour.  On  the  four  different  periods 
when  the  hardest  work  was  done  the  heat  production  per  hour  was 
608,  616,  625,  and  626  calories,  respectively.  During  these  severe 
work  periods  the  n mount  of  t  ransformation  of  external  muscular  work 
reached  116  calories.  The  resting  metabolism  was  independently 
determined  for  bol  h  series  of  experiments,  and  in  computing  the  excess 
of  heat  produced  above  the  resting  metabolism,  the  values  found  for 

during  each  series  were  used.  The  heat  produced  above  the  rest- 
ing metabolism  is  recorded  in  the  table.  The  efficiency  varied  from 
19.68  to  22.17.  averaging  21  per  cent. 

W  V!  II:    \  AI-OIMZKI). 

The  primary  object  of  the  measurements  of  water  vaporized  in  these 

erimenta  was  to  obtain  the  heat   production,  since  a  part  of  the 

heat  production  i    expended  in  vaporizing  water  from  the  lungs  and 


32 

skin  (0.592  calorie  per  gram  of  water).  As  a  matter  of  fact,  during 
the  riding  periods  his  clothing  was  saturated  with  perspiration  and  he 
was  literally  reeking  with  perspiration  when  he  left  the  chamber. 
The  sensible  perspiration,  however,  does  not  modify  in  any  way  the 
heat  measurement.  In  the  form  of  calorimeter  used  in  these  experi- 
ments a  current  of  cold  water  is  passed  through  a  heat-absorbing  sys- 
tem inside  the  chamber.  The  temperature  of  the  water  during  these 
work  experiments  is  nearly  0°  C,  and  consequently  there  is  a  condensa- 
tion of  moisture  from  the  air  on  these  absorbers.  This  amounted, 
therefore,  to  a  distillation  of  water  from  the  body  of  the  subject  upon 
the  absorbers,  but  obviously  only  the  water  that  was  vaporized  and 
not  again  condensed  affects  the  heat  measurements,  and  accordingly 
the  values  for  water  vaporized  have  no  significance  whatever  as  indexes 
of  the  amount  of  sensible  and  insensible  perspiration,  except  in  the  rest 
experiments.  The  values  recorded  in  the  table  under  the  head  of 
water  vaporized  are  very  misleading.  There  was  no  sensible  perspira- 
tion during  either  of  the  rest  experiments. 

While  from  the  amount  of  water  condensed  on  the  absorbers  and  the 
increase  in  weight  of  the  underclothing  it  is  possible  in  most  experi- 
ments with  muscular  work  to  obtain  data  regarding  the  total  sensible 
and  insensible  perspiration,  in  these  series  of  experiments  provision 
could  not  be  made  for  a  satisfactory  study  of  these  excretions,  and 
accordingly  we  were  obliged  to  forego  a  study  of  the  perspiration. 

CARBON    DIOXID    EXCRETED. 

Muscular  work  resulting  from  the  transformation  of  body  material 
is  accompanied  by  an  increase  in  the  excretion  of  carbon  dioxid  and 
absorption  of  oxygen.  Of  these  two  factors,  the  carbon  dioxid  ex- 
cretion has  been  more  commonly  studied.  In  all  the  experiments 
with  N.  B.  the  carbon  dioxid  was  accurately  measured.  The  results 
computed  to  the  excretion  per  hour  have  been  previously  given 
(table,  p.  31).  It  may  be  seen  from  the  data  that  during  the  October 
experiments  this  subject  excreted  28.56  grams  of  carbon  dioxid  per 
hour  when  at  rest.  During  the  corresponding  January  experiment 
he  excreted  29.41  grams  per  hour,  an  agreement  that  is  most  satis- 
factory considering  the  length  of  time  between  the  two  experiments. 

The  most  marked  influence  of  excessive  muscular  work  on  the 
carbon  dioxid  excretion  is  seen  from  the  amounts  eliminated  on  the 
days  of  severe  muscular  work.  These  amounts  frequently  exceeded 
200  grams  per  hour.  Indeed,  during  the  first  period,  January  23 
the  amount  of  carbon  dioxid  eliminated  was  231.03  grams.  This  if 
nearly  eight  times  the  elimination  during  rest.  A  moderate  degree 
of  muscular  activity,  such  as  that  produced  by  riding  the  ergometer 
without  resistance,  i.  e.,  during  coasting,  approximately  doubled  the 


33 

carbon  dioxid  output,  and  here,  too,  it  is  of  interest  to  note  that  the 
values  obtained  during  coasting  in  October  and  January  were  nearly 
the  same,  i.  e.,  62.15  and  63.50  grains,  respectively. 

The  relation  between  the  carbon  dioxid  output  and  the  heat  produc- 
t  i(  >n  are  very  evident  if  the  values  shown  in  columns  c  and  e  (table,  p.  31 ) 
are  compared.  The  large  heat  production  is  accompanied  by  a  large 
carbon  dioxid  elimination.  An  inspection  of  the  figures,  however, 
shows  that  the  relation  between  the  carbon  dioxid  and  the  heat  pro- 
duction is  not  constant.  Thus,  during  the  first  work  period  of  the 
experiment  on  January  23,  when  the  maximum  amount  of  carbon 
dioxid  was  eliminated,  i.  e.,  231.03  grams,  there  were  607.99  calories 
of  heat  produced,  while  during  the  second  work  period  of  the  same 
day,  when  a  maximum  heat  production  was  obtained,  namely,  626 
calories,  the  carbon  dioxid  production  was  actually  20  grams  less. 
This  serves  to  show  the  difficulties  of  computing  accurately  the  heat 
production  from  the  carbon  dioxid  output.  While,  therefore,  the 
carbon  dioxid  output  is  markedly  and  immediately  influenced  by 
excessive  muscular  exertion,  it  is  not  safe  to  assume  that  there  is 
constant  relation  between  the  carbon  dioxid  output  and  the  heat 
production. 

OXYGEN    ABSORBED. 

Although  during  the  October  experiments  the  measurements  were 
not  satisfactory,  in  the  second  series  of  experiments  with  N.  B.  it 
was  possible  to  measure  the  oxygen  absorption  with  reasonable  accu- 
racy. The  same  influence  on  the  quantities  of  oxygen  absorbed  that 
was  noted  on  the  carbon  dioxid  elimination  may  be  seen  here.  The 
excessive  muscular  work  increases  markedly  the  oxygen  absorption. 
But  an  inspection  of  the  figures  shows  that,  at  least  as  far  as  these 
results  go,  there  is  not  an  absolute  uniformity  between  the  ratios  of 
tin-  oxygen  absorbed  and  the  heat  produced.  During  rest  this  sub- 
ject absorbed  22.77  grams  of  oxygen  per  hour.  During  muscular 
work  the  oxygen  absorption  increased  in  one  experiment  to  183.38 
grams  per  hour. 

CONDITIONS    INSIDE   THE    RESPIRATION    CHAMBER. 

Although  the  subjects  perspired  freely  during  the  work  periods, 

and  especially  in  the  case  of  X.  B.,  the  clothing  was  drenched  with 

perspiration,  yet  the  nature  of  the  special  form  of  calorimeter  used 

, re ven fed  any  excessive  accumulation  of  water  vapor  inside  the 

(  jpiratios  chamber.     The  water  entering  the  heat-absorbing  pipes 

very  cold,  and  hence  the  moisture  condensed  out  of  the  air  on 

these  pipes  and  collected  in  troughs  suspended  under  the  absorbers. 

Thus,  while  there  was  an  enormous  evaporation  of  water  from  the 

70076— Bull.  208—09 3 


34 

lungs  and  skin  of  the  subject,  so  rapidly  was  it  condensed  on  the  heat 
absorbers  that  the  humidity  of  the  air  inside  the  chamber  rarely  rose 
above  70  per  cent. 

There  was  entire  absence  of  air  currents,  at  least  such  as  were 
perceptible  to  the  man.  The  total  quantity  of  air  entering  the  cham- 
ber amounted  to  but  75  liters  per  minute,  approximately  3  cubic  feet, 
and  this  entered  in  such  a  manner  as  to  be  directed  toward  the  floor 
of  the  calorimeter.  By  means  of  the  heat-absorbing  appliances  the 
temperature  of  the  calorimeter  was  kept  invariably  at  19°  to  20°  C, 
and  inasmuch  as  the  humidity  did  not  rise  to  any  excessive  point  the 
subjects  underwent  no  discomfort  as  a  result  of  defective  thermolysis. 
There  was  no  air  current  inducing  rapid  evaporation  such  as  is  com- 
mon when  riding  a  bicycle  in  the  open  air,  and  moreover  there  was 
no  wind  resistance. 

GENERAL  DISCUSSION  OF  RESULTS. 

PERSONAL   IMPRESSIONS    OF    THE     SUBJECTS    OF   THE 
EXPERIMENTS. 

So  far  as  can  be  judged  from  the  personal  impressions  of  the  sub- 
jects, no  especial  discomfort  was  noticed  in  any  of  the  experiments. 
All  complained  of  the  monotony,  and  N.  B.  stated  that  he  had  never 
worked  as  hard  in  his  life,  not  even  in  the  most  severe  race,  as  he 
did  during  the  periods  when  the  ergometer  was  magnetized  with  a 
current  of  1.25  amperes.  The  psychical  stimulus  of  the  crowd  of 
spectators  at  a  race  was  wanting,  and  the  riding  became  very 
tedious. 

When  the  ergometer  was  magnetized  with  a  current  of  0.9  ampere 
the  subject  felt  that  he  was  doing  about  the  work  that  would  be  called 
for  in  the  continuous  riding  of  a  six-day  race.  Although  a  personal 
impression,  this  observation  is  of  much  value  in  subsequent  dis- 
cussion. 

SUMMARY  OF  RESULTS  OF  MUSCULAR  WORK  EXPERIMENTS. 

The  special  purpose  of  this  study  being  to  observe  the  relationship 
between  the  total  heat  production  and  the  heat  equivalent  of  external 
muscular  work,  the  results  of  all  the  experiments  have  been  calculated 
to  amounts  per  hour  and  the  abstract  of  the  results  recorded  in  the 
following  table. 


35 


Summary  of  results  of  muscular  work  experiments. 

[Amounts  per  hour.] 


Subject. 


(a) 


Current 
through 
magnet. 


(6) 

Revo- 
lutions 

per 
minute. 


<n 


Resting. 


W 


Total 
heat  pro- 
duced. 


(*) 

Heat 
equiva- 
lent of 
muscu- 
lar work. 


Mechanical  effi- 
ciency. 


(/) 

eXIOO 

d 


(?) 

eXIOO 
d-o 


J.  C.  W.,  average  of  six  days 

B.  F.  D.,  average  of  three  experi- 
ments   

A.  L.  L..  average  of  six  days 

A.  L.  L..  extra  severe  work  one 
day 

A.  L.  L.,  coasting,  average  of  two 
days 

E.  V.  S.,  one  day 

X.  B..  average  of  four  experiments 

X.  B.,  average  of  two  experiments 

X.  B.,  average  of  two  experiments. 

X.  B. .  one  experiment  

X.  B..  coasting,  average  of  two 
experiments 


A  111  inn*. 
1.25 

1.25 
1.25 

1.25 


Calories. 

a  112 


51 

i  106 
&106 

105 

51 

SI 
7(i 
70 

"117 

|    *92 

7s 

J 

83 

Calories. 
339 


318 
299 


135 
399 
619 
471 
401 
3S2 


Calories. 


Per  cent. 
14.5 


14.2 
12.7 


Per  cent. 
21.6 


21.2 
19.7 


51 
112 
79 
05 
60 


12.8 
18.1 
16.8 
16.2 

15.7 


rf  18. 1 
21.3 
20.8 
21.0 

20.7 


a  Average  of  four  days. 

b  Average  of  two  days. 

<"  Average  based  on  resting  output  (1,400  calories)  assumed.    See  page  29. 

<i  Xot  included  in  average. 

<■  Average  of  two  experiments. 

In  the  majority  of  the  experiments  the  strength  of  the  current  used 
for  magnetizing  the  fields  was  1.25  amperes,  although  three  experi- 
ment- with  X.  B.  were  made  with  weaker  currents.  The  resting 
metabolism  was  taken  as  the  average  of  such  experiments  as  were 
available  for  the  different  individuals,  save  in  the  case  of  E.  F.  S., 
where  ,i  resting  metabolism  estimated  from  a  large  number  of  experi- 
ments with  individuals  of  a  similar  weight  was  taken.  In  averaging 
the  experiments  with  B.  F.  D.  the  total  heat  produced  during  rest 
(with  food)  was  taken  as  the  average  of  three  experiments,  two  of 
twelve  hours  each  and  one  of  six  hours. 

The  resting  metabolism  for  the  severe  work  experiment  was  taken 
;i-  the  heat  production  per  hour  for  the  rest  period  corresponding 
t<>  the  work  period.  The  heat  production  during  coasting  was  also 
recorded  for  this  subject.  With  the  subject  A.  L.  L.  the  average 
results  of  the  two  ordinary  work  experiments  are  given,  as  is  also 
the  result  of  the  severe  work  experiment. 

In  nil  the  experiments  except  those  with  X.  B.  it  must  be  borne  in 
mind  thai  the  subjects  were  not  continuously  at  work  during  the 
experimental  period.  Thus  in  the  experiments  with  J.  C.  W.  each 
experimental  period  covered  twelve  hours,  while  (he  actual  work 
occupied  only  eight  of  these  twelve  horns.  Similarly,  the  work 
periods  with  A.  L.  I>.  and  B.  F.  I),  were  only  about  eight  out  of  the 
[ve  hour-.  Even  in  the  extra  severe  work  of  A.  L.  L.  the  actual 
working  time  was  much  less  than  the  experimental  periods.  How- 
ever, since  in  the  computation  of  the  results  the  resting  metabolism 


36 

is  deducted  from  the  total  heat  produced,  the  fact  that  the  work  was 
not  continuous  throughout  the  experimental  period  does  not  affect 
the  results. 

On  the  other  hand,  in  all  the  experiments  with  N.  B.  the  work 
period  and  the  period  of  experiment  were  coincident.  For  that 
reason  the  total  heat  production  per  hour  was  very  much  larger  with 
this  subject  than  with  any  other. 

MECHANICAL  EFFICIENCY  OF  THE  HUMAN  BODY. 

METHODS  OF  CALCULATION  AND  RESULTS. 

Two  methods  of  computing  the  mechanical  efficiency  may  be  used. 
By  the  first  method  the  heat  equivalent  of  muscular  work  is  com- 
pared to  the  total  heat  production.  By  the  second  method  the  heat 
equivalent  of  muscular  work  is  compared  to  the  total  heat  production 
less  the  resting  metabolism.  This  latter  method  has  been  more 
commonly  used,  but  the  results  by  both  methods  of  computation  are 
given  in  the  table.  Since  the  experimental  periods  were  not  always 
coincident  with  the  working  periods,  the  results  are  more  comparable 
when  considered  on  the  latter  basis,  and,  consequently,  the  heat 
equivalent  of  external  muscular  work  is  compared  with  the  total 
heat  production  less  the  resting  heat  output.  The  results  show  a 
striking  uniformity  in  the  mechanical  efficiency  of  all  of  these  men, 
averaging  not  far  from  20.9  per  cent.  The  lowest  was  that  observed 
in  the  case  of  E.  F.  S.,  18.1  per  cent,  but,  as  has  been  shown  above, 
the  resting  value  for  this  subject  was  estimated  and  not  measured. 

Perhaps  the  most  surprising  feature  of  these  results  is  that  the 
professional  bicycler,  N.  B.,  showed  practically  no  higher  efficiency 
than  the  other  subjects.  While  J.  C.W.  was  a  trained  bicycler,  A.  L.  L. 
was  entirely  unfamiliar  with  bicycle  riding  before  he  began  these 
experiments,  and  both  B.  F.  D.  and  E.  F.  S.  had  had  but  little  experi- 
ence in  riding  the  bicycle.  That  the  trained  muscles  of  the  profes- 
sional bicycler  should  not  have  shown  a  greater  efficiency  than  did 
the  muscles  of  the  younger  and  less  experienced  men  is  indeed  sur- 
prising. It  is,  however,  to  be  borne  in  mind  that  the  experiments 
are  not  strictly  comparable,  and  while  our  experience  would  indicate 
that  substantially  the  same  efficiency  would  be  found  with  the 
other  men  in  experiments  on  the  plan  of  those  made  with  N.  B., 
nevertheless  such  experiments  should  be  made  before  a  final  con- 
clusion is  drawn  regarding  the  effect  of  training. 

It  should  be  added  that  the  experiments  in  which  the  resting  value 
with  N.  B.  was  obtained  were  conducted  on  a  somewhat  different 
plan  than  those  with  the  other  subjects,  in  that  the  subject  was  very 
quiet  and  did  not  have  the  freedom  of  movement  allowed  the  other 
men. 


37 

The  computation  of  the  mechanical  efficiency  of  a  man  is  beset 
with  certain  difficulties  not  experienced  with  the  ordinary  form  of 
heat  engines.  Thus  the  body  requires  a  certain  amount  of  energy  to 
maintain  it  in  the  resting  condition.  This  is  not  far  from  2,300 
calories  per  day,  although  the  amount  differs  with  the  individual. 

The  work  performed  by  the  body  may  be  said  to  consist  of  two 
kinds,  internal  and  external.  Of  these  two,  it  is  possible  for  us  in 
these  experiments  to  measure  only  the  external  work  expended  in 
riding.  From  the  data  given  in  the  statistics  of  the  experiments  it 
is  possible  to  find  what  proportion  of  the  energy  produced  above  the 
resting  metabolism  can  be  converted  into  external  muscular  wTork, 
and  on  this  basis  the  proportion  is  very  high.  On  the  contrary,  it 
may  be  stated  that  the  percentage  should  be  based  upon  the  total 
heat  production  for  the  day,  and  thus  involve  the  heat  production 
during  rest.  Calculated  on  this  basis,  the  efficiency  is  obviously 
very  much  lower.  The  degree  to  which  the  calculation  of  the  per- 
centage efficiency  would  be  affected  by  including  the  resting  heat 
production  depends  in  large  part  upon  the  total  heat  production 
during  the  work  experiments.  If  the  heat  production  is  very  large, 
the  including  of  the  heat  of  resting  metabolism  does  not  influence  the 
final  result  to  anything  like  the  extent  that  it  would  if  the  total  heat 
production  during  work  wrere  small.  This  is  especially  noticeable 
in  the  experiment  with  A.  L.  L.,  in  which  he  worked  for  a  good  part  of 
the  day.  The  percentage  efficiency  computed  on  the  basis  of  heat 
production  above  resting  metabolism  is  20.8  per  cent,  while  the  per- 
cent age  of  the  total  energy  transformed  into  external  muscular  work 
is  14.1  per  cent..  In  the  table  on  page  35,  column  f,  the  results  for 
all  the  experiments  are  included,  showing  the  mechanical  efficiency 
of  the  mail  based  upon  the  total  heat  production  of  the  day. 

While  it  is  impossible  to  measure  the  thermal  equivalent  of  the 
internal  muscular  wrork,  it  is  also  impossible  to  measure  the  thermal 
equivalent  of  the  external  muscular  exertion  involved  in  preparing 
the  ergometer  to  tide,  dressing  and  undressing,  mounting  and  dis- 
mounting, but  it  would  he  of  interest  to  compute  the  efficiency  of 
the  subjects  deducting  not  only  the  heat  production  during  rest 
hut  also  the  heat  product  ion  incidental  to  the  preparation  of  the 
ergometer,  etc. 

The  same  difficulties  thai  are  encountered  in  attempting  to  measure 

the  heal    equivalent    of   the  extraneous  muscular  exertion   Incidental 

to  preparation  of  the  wheel  are  likewise  encountered  in  determining 
iratel)    the   thermal   equivalent  of    the   internal   friction   of  the 
muscles  of  the  leg  when  riding  the  bicycle  ergometer.     The  experi- 
ments   ill    which    the   subject    rode   or   coasted    with     dec    leg    motion 

were  made  with  the  specific  purpose  of   permitting  the  deduction 
from  the  total  heal  outpul  of  the  beat   required  to  rotate  the  ergom- 


38 

eter  without  resistance  other  than  the  slight  amount  due  to  me- 
chanical friction.  A  series  of  computations,  therefore,  is  of  interest 
to  show  the  actual  heat  production  necessary  to  produce  the  heat 
of  external  muscular  work  recorded  in  these  experiments  over  and 
above  that  required  to  rotate  the  ergometer  without  resistance. 
These  data  also  furnish  the  means  for  computing  mechanical  ef- 
ficiency on  another  basis. 

"COASTING"  ON  A  BICYCLE. 

In  the  process  of  riding  the  ergometer  without  resistance,  which 
has  here  been  called  "  coasting,"  two  factors  come  into  play.  First, 
the  energy  required  to  overcome  the  friction  of  the  machine,  and 
second,  the  internal  friction  of  the  muscles.  From  the  construction 
of  the  bicycle  it  can  readily  be  seen  that  the  weight  of  the  two  legs 
on  the  pedals  is  practically  counterbalanced,  so  that  one  leg  in 
descending  counterbalances  the  other  leg  when  raised  and  thus  no 
mechanical  work  is  called  for.  From  a  calibration  of  the  ergometer 
in  which  the  machine  was  placed  inside  the  respiration  chamber 
and  rotated  without  electrical  resistance,  it  was  found  that  each 
revolution  of  the  pedals  produced  sufficient  friction  to  correspond 
to  0.001547  calorie  of  heat.  Therefore  in  coasting  the  different  sub- 
jects must  have  performed  this  amount  of  work  for  each  revolution. 
With  two  subjects  the  amount  of  heat  eliminated  during  a  coasting 
period  was  determined.  A.  L.  L.  coasted  eight  out  of  twelve  hours  on 
two  days,  and  the  heat  production  per  hour  was  found  to  be  135 
calories.  N.  B.  coasted  for  shorter  periods,  but  two  experiments 
showed  an  average  of  182  calories  per  hour.  That  these  two  values 
do  not  compare  is  due  to  the  fact  that  during  the  hours  that  N.  B. 
was  coasting  he  worked  continuously,  while  with  A.  L.  L.  the  figure 
represents  the  value  for  eight  hours  actual  coasting,  divided  by 
twelve,  the  number  of  hours  in  the  experimental  period.  As  a 
matter  of  fact,  while  coasting,  N.  B.  rode  at  a  faster  rate  than  did 
A.  L.  L. 

CALCULATION    OF    MECHANICAL    EFFICIENCY    BASED    ON    COASTING    ON 

A    BICYCLE. 

In  computing  the  efficiency  of  the  body  as  a  machine,  it  may  be 
of  value  to  calculate  this  efficiency  not  only  by  deducting  the  resting 
heat  output  from  the  total  heat  production  during  a  work  period, 
but  also  by  deducting  the  heat  output  during  coasting.  The  dif- 
ference between  the  total  output  during  severe  work  and  that  during 
the  coasting  period  corresponds,  then,  to  the  energy  required  to 
transform  the  external  muscular  work  into  heat.  In  three  experi- 
ments with  N.  B.  with  a  current  of  1.25  amperes  the  average  heat 


production  per  hour  was  617  calories;  the  heat  equivalent  of  muscular 
work  was  115  calories;  the  coasting  value  was  182  calories.  Since 
in  coasting,  however,  the  friction  of  the  ergometer  corresponds  to 
8  calories  per  hour,  it  is  necessary  not  only  to  deduct  from  the  total 
heat  output  the  coasting  heat  output,  but  also  to  deduct  from  the  heat 
equivalent  of  muscular  work  the  heat  equivalent  of  the  friction  of  the 
machine  during  coasting,  i.  e.,  8  calories.  The  results  for  the  differ- 
ent series  of  experiments  with  N.  B.  are  recorded  in  the  table  which 
follows : 

Mechanical  efficiency  based  on  coasting. 

[Amounts  per  hour.] 


(o) 


(t) 


Subject. 


(c) 

Heat 

Current,    tions  per  P*d 
minute.  ;    ^™f 


Revolt!- 


(d) 

(«) 

(J) 

Esti- 

Heat 

Beat 

mated 

equiv- 

produced 

heat  re- 

alent  of 

during 

quired 

work 

coasting. 

for  work 

(less  fric- 

<c-4). 

tion). 

Calories. 

Calories. 

Calories. 

182 

435 

«  107 

167 

304 

72 

153 

LM^ 

58 

171 

211 

52 

135 

im 

35.5 

(9) 

Effi- 
ciency. 
/X100 


N.  B... 
N.  B... 
N.  B... 
X.  B... 

A.  L.  L. 


.4  mperes. 

1.25 
.90 
.80 
.70 

1.25 


Calorics. 
a  617 
471 
401 
382 
299 


Per  cent. 
24.6 
23.7 
23.4 
24.6 
21.6 


a  Average  of  three  experiments.    Does  not  include  experiment  of  October  21,  1904. 

In  column  e  is  given  the  total  heat  production  less  the  heat  pro- 
duction during  coasting,  and  in  column  f  the  heat  equivalent  of 
muscular  work  due  to  the  electric  brake,  i.  e.,  the  heat  equivalent  of 
muscular  work  less  the  heat  equivalent  of  the  friction  during  coasting. 
Assuming  a  rate  of  eighty-three  revolutions  per  minute,  the  heat 
equivalent  of  the  friction  may  be  readily  computed  as  follows: 
83x60  =  4,980  revolutions  per  hour.  This  multiplied  by  the  factor 
0.01)1547  gives  a  total  heat  production  per  hour  at  the  rate  of  eighty- 
three  revolutions  per  minute  of  about  8  calories,  and  consequently 
the  work  to  overcome  the  electrical  resistance  of  1.25  amperes  was 
107  calories.  We  may  then  say  that  of  the  435  calories  required  to 
overcome  the  electrical  brake  effeel  of  the  ergometer  107  were  trans- 
formed into  the  heat  equivalent  of  external  muscular  work.  The 
efficiency  computed  on  this  basis  is  24.6  per  cent. 

Calculations  al  other  intensities  of  magnetization  of  the  fields  of 
the  magnet  gave  similar  results.  Unfortunately,  in  the  other  series 
of  experiments  the  rate  per  minute  varied  somewhat,  and  in  com- 
puting lli*'  values  in  column  '/  it  was  assumed  that  the  coasting  rate 
;it  the  same  number  of  revolutions  per  minute  would  he  proportional 
to  the  rates  of  revolution.     Thus  al  0.9  ampere  the  heat  production 

during  e.,;i~t  j||'_r  .it  the  Hile  of  70  fe  vol  1 1 1  io!l>  per  lllillllte  W  ;|S  Com- 
puted as  follow-:  76:83  x:182.  ,\  107.  The  other  computations 
are  identical  with  those  lor  the  experiments  with  1.25  amperes. 


40 

Computed  on  this  basis,  the  percentage  efficiency  is  considerably 
higher  than  on  either  of  the  other  bases,  and  there  is  not  the  uni- 
formity in  the  efficiency  percentage  which  is  noted  in  the  other 
calculations.  Two  factors  enter  into  this  method  of  computation 
which  are  not  as  perfectly  established  as  they  should  be.  First, 
the  energy  of  friction  per  revolution  of  the  pedals  without  electrical 
resistance  has  been  determined  in  only  one  experiment,  and  obviously 
the  value  to  be  deducted  from  the  heat  equivalent  of  muscular  work 
in  the  different  experiments,  especially  with  N.  B.,  may  contain  a 
considerable  error.  Again,  it  is  assumed  that  the  heat  output  during 
coasting  would  be  proportional  to  the  number  of  revolutions  per 
minute. 

The  experiment  with  A.  L.  L.  permits  of  a  similar  comparison  of 
the  mechanical  efficiency  obtained  by  deducting  the  heat  output 
during  coasting  from  the  total  heat  output.  The  values  are  given 
in  the  lower  part  of  the  table.  In  this  experiment  the  rates  per 
minute  were  the  same  during  both  the  work  and  the  coasting  period. 
There  is,  however,  a  marked  difference  in  that  the  riding  was  done 
irregularly  throughout  the  day  and  occupied  but  eight  of  the  twelve 
experimental  hours ;  the  number  of  revolutions  made  during  coasting 
was  likewise  distributed  throughout  the  twelve  hours  of  the  experi- 
ment, but,  on  the  other  hand,  they  were  the  same  in  number  as  those 
during  the  work  experiment.  While  there  is  distinct  objection  to 
comparing  the  experiments  with  A.  L.  L.  with  those  made  with 
N.  B.,  the  results  show  that  the  percentage  efficiency  of  A.  L.  L. 
computed  on  this  basis  is  noticeably  less  than  that  with  N.  B.  In 
so  far,  then,  as  the  results  of  these  experiments  show,  the  profes- 
sional bicycler  N.  B.  had  a  somewhat  higher  efficiency  than  the  other 
subject  when  this  efficiency  is  computed  by  deducting  from  the 
total  heat  output  during  work  the  output  during  coasting. 

INTERNAL    FRICTION    OF   LEG. 

In  the  operation  of  coasting  the  subject  has  to  overcome  the 
friction  of  the  machine  as  well  as  the  internal  friction  of  the  leg, 
and  from  the  two  experiments  with  A.  L.  L.  and  N.  B.  an  approxi- 
mate indication  of  the  work  of  internal  friction  may  be  had.  A.  L.  L., 
riding  the  ergometer  approximately  eight  hours  per  day  had  a  rate 
of  speed  of  51  revolutions  per  minute  and  produced  on  two  days 
1,585  and  1,669  calories  of  heat,  respectively.  The  resting  metab-' 
olism  was  taken  as  1,277  calories,  and  hence  the  excess  over  resting 
was  on  the  first  day  308  and  on  the  second  392  calories.  From  the 
total  number  of  revolutions  and  the  heat  of  friction  per  revolution 
it  is  calculated  that  the  work  of  friction  of  the  machine  amounted  to 
29.9  calories.  From  the  experiments  made  with  a  number  of  men 
and  here  reported,  it  is  seen  that  the  mechanical  efficiency  of  the 


41 

man  is  not  far  from  20  per  cent,  and  hence  the  actual  heat  output 
required  to  rotate  the  machine  and  overcome  the  work  of  friction 
would  be  the  heat  equivalent  of  the  friction  X  5,  or  in  these  two 
experiments  140.")  calories.  Deducting  this  value  from  the  differ- 
ence between  the  coasting  and  the  resting  metabolism  wives  the 
value  for  the  work  of  internal  friction  of  the  legs.  For  the  two  days 
it  is  158.5  and  242.5  calories,  respectively.  The  agreement  is  far 
from  satisfactory.  On  the  first  day,  therefore,  of  the  total  excess 
heat  above  the  resting  metabolism,  approximately  one-half  was 
required  to  overcome  the  friction  of  the  machine  and  a  little  over 
one-half  to  overcome  the  work  of  internal  friction.  On  the  second 
day  60  per  cent  of  the  excess  heat  was  required  for  the  work  of 
internal  friction.  In  one  experiment  with  N.  B.  the  results  are  as 
follows:  The  average  rate  per  minute  when  coasting  was  83,  the 
re-ting  metabolism  92  calories  per  hour,  coasting  182  calories,  and 
the  excess  over  coasting  90  calories.  The  computation  of  the  work 
of  friction  shows  it  to  be  8  calories  per  hour,  and  the  energy  required 
tn  produce  this  work  was  consequently  40  calories.  This  deducted 
from  the  excess  of  coasting  over  resting  yields  50  calories  per  hour 
as  the  work  of  internal  friction.  These  results  with  N.  B.  are  com- 
parable with  those  of  A.  L.  L.  only  in  so  far  as  the  proportion  of  the 
excess  heat  is  due  to  work  of  internal  friction.  On  the  two  experi-. 
mcuts  with  A.  L.  L.  the  work  of  internal  friction  was  51.5  and  61.9 
per  cent  of  the  total  excess  over  resting  metabolism,  respectively, 
while  with  X.  B.  the  work  of  internal  friction  was  55.6  per  cent  of 
the  excess  over  the  resting  metabolism. 

Heat  dm  v,  internal  friction  of  legs  in  rousting  expi  riments  with  A.  L.  L.  and  N.  B. 


Bnbjecl 


- 


(«) 

lie; 
(6) 

Revolu- 

tions 

per 

infinite. 

Rest. 

Calories. 

51 

1 .  277 

:,t 

1.277 

92 

l  [eat  production. 


Friction  of  machine, 


(c)  (d) 

Excess 

Coasting.       over 
resting 

(c— b). 


Calories.  Calories. 

1,685  308 
1,669 

|S2  90 


(e) 

Heal 

equiva- 
lent of 
f  riot  ion. 


Culm  its. 

29. 9 

2' I.!  I 
s  O 


(/) 

Esti- 
mated 

heat  out- 
put 
(eX5). 


Calories. 
149. 5 

i  ».6 

in  n 


Heal  (lur  to  friction 
of  legs. 


iff) 


Amount 

I-/        /,. 


L58.5 

212.:, 

.Mill 


(ft) 

Propor- 
tion of 
excess 
during 
coasting 
(0X100) 
-i-d. 


I'i  i  n  nl . 

51.6 
61.9 

;,.-,.  6 


HI  •  per  hour. 


MM  II  \\K   \l.     l.l  I  [CIENC1       KB      \l  l  ECTED     BT 

INl'KNsnv    or    WORK. 


\  V.RYING     DEGREES     (>!•' 


It  has  been  commonly  believed  thai  the  human  body  in  common 
with  the  ordinary  steam  engine  varies  its  efficiency  with  the  load. 
ror  each  engine  th<T<-  i-  ;i  l<>;i<l  ;tt  which  the  maximum  efficiency  is 


42 


obtained.  In  certain  of  these  experiments  the  data  regarding  the 
heat  production  and  heat  of  external  muscular  work  are  sufficiently 
complete  to  furnish  evidence  regarding  the  effect  of  load  on  the 
efficiency  of  the  human  machine. 

With  increasing  load  there  was  increased  total  heat  production  and 
increased  heat  of  external  muscular  work,  and  it  remains,  therefore, 
to  consider  what  effect  on  the  efficiency  was  produced  by  the  varia- 
tions in  load. 

While  the  use  of  the  resting  metabolism  as  a  base  line  for  the  com- 
putation of  the  efficiency  is  open  to  the  objections  stated  above,  for 
the  calculation  of  the  effect  of  increased  load  the  data  are  sufficient 
and  much  less  open  to  criticism.  Thus  in  order  to  increase  the  heat 
of  external  muscular  work  by  5  calories  per  hour  the  current  through 
the  electro-magnet  was  increased  to  0.7  to  0.8  ampere  and  the  total 
heat  production  per  hour  rose  from  382  calories  with  0.7  ampere  to 
401  calories  with  0.8  ampere.  Coincidently,  the  heat  equivalent 
of  external  muscular  work  increased  60  to  65  calories  per  hour.  Thus 
an  increase  of  5  calories  in  the  external  muscular  work  was  accom- 
panied by  or  necessitated  an  increased  heat  production  amounting 
to  19  calories.  A  simple  calculation  shows  that  of  the  increased  heat 
production  26  per  cent  was  converted  into  heat  of  external  muscular 
work. 

Similar  computations  for  the  various  increases  in  load  are  given 
in  the  following  table,  the  data  being  obtained  from  the  last  part  of 
the  table  on  page  35: 

Effect  of  increasing  external  work  on  body  efficiency. 


(a) 

Increase  in 

magnetization 

from — 

Increase  of 
total  heat. 

(C) 

Increase  of 

heat  of 

external 

work. 

Efficiency. 

(CX100) 

b 

Amperes. 

0.7  to  0.8 
.7  to    .9 
.7  to  1.25 
.8  to    .9 
.8  to  1.25 
.9  to  1.25 

Calories. 

19 

89 

237 

70 

218 

148 

Calories. 
5 
19 
52 
14 
47 
33 

Per  cent. 
26.0 
21.3 
22.0 
20.0 
21.5 
22.3 

Aside  from  the  value  for  the  increase  from  0.7  to  0.8  ampere,  i.  e., 
26  per  cent,  all  the  results  are  remarkably  constant,  showing  that  the 
increase  of  load  does  not  materially  affect  the  efficiency  of  the  body 
as  a  machine.  Under  all  the  conditions  of  work  in  these  experiments 
the  body  was  able  to  transmit  about  21  per  cent  of  the  increased  heat 
incidental  to  the  increased  load  into  heat  of  external  muscular  work. 

In  connection  with  these  computations  it  should  be  pointed  out 
that  a  possible  disturbing  factor  is  the  fact  that  the  speed  per  minute 
was  not  uniform  with  all  degrees  of  magnetization  of  the  field,  while 


43 

it  is  highly  probable  that  similar  results  would  have  been  obtained 
in  a  series  of  experiments  in  which  a  constant  speed  was  maintained 
with  all  grades  of  resistance.  The- experiments,  unfortunately,  were 
not  made  under  ideal  conditions  for  studying  this  point,  and  hence 
that  possible  error  must  be  borne  in  mind. 

Many  other  methods  of  using  these  figures  in  computations  of  the 
efficiency  of  each  man  and  in  comparing  the  results  under  different 
conditions  might  be  devised,  but  it  is  believed  that  the  comparisons 
here  made  are  all  that  the  figures  justify.  It  is  made  clear  from 
these  experiments  that  the  problem  of  studying  the  mechanical  effi- 
ciency of  a  man  is  a  most  interesting  one.  So  far  as  we  are  aware, 
no  method  as  yet  published  furnishes  a  result  as  satisfactory  and 
mathematically  accurate  as  does  the  use  of  the  bicycle  ergometer  and 
the  respiration  calorimeter. 

COMPARISON  OF  RESULTS  WITH  COMPUTATIONS  OF  MECHANICAL 
EFFICIENCY  OF  SIX-DAY  BICYCLE  RIDERS. 

Unusual  interest  has  been  attached  to  the  attempts  to  compute  the 
heat  equivalent  of  work  done  by  six-day  bicycle  riders  in  their  long- 
continued  muscular  strain,  and  also  to  compute  the  percentage  effi- 
ciency of  these  men.  R.  C.  Carpenter0  computed  that  on  the  six 
days  of  the  bicycle  race  held  in  December,  1898,  C.  W.  Miller  pro- 
duced 4,917,  3,471,  2,917,  2,631,  2,892,  and  1,786  calories  of  external 
muscular  work.  On  these  days  Miller  rode  from  23}  to  14}  hours 
per  day.  In  attempting  to  compute  the  mechanical  efficiency  of  this 
man,  Carpenter  was  much  handicapped  by  the  fact  that  no  measure 
was  available  of  the  amount  of  body  fat  lost  during  the  period, 
and  although  the  food  consumed  was  accurately  measured,  never- 
theless the  total  energy  transformations  could  not  be  accurately 
computed  owing  to  the  absence  of  data  regarding  the  losses  of  body 
fat.  Making  no  allowance  for  the  body  fat,  Carpenter  computes 
apparent  efficiencies  of  over  60  per  cent  in  the  case  of  Miller,  and 
of  nearly  45  per  cent  in  the  case  of  another  rider.  In  the  experiments 
here  reported  the  total  heat  production,  as  well  as  the  energy  of 
mechanical  work,  is  available.  Mr.  Butler,  a  professional  -rider,  was 
of  the  opinion  thai  with  the  ergometer  magnetized  with  a  current 
of  0.9  ampere,  t  he  resist  ance  was  very  much  t  he  same  as  that  experi- 
enced during  a  six-day  race,  and  the  experiment  showed  that  this 
resulted  in  the  product  ion  of  7*.)  calorics  of  heat  per  hour  in  the  form 
of  external  muscular  work.  In  order  to  transform  this  amount  of 
mat  muscular  work,  \.  B.  produced  a  total  of  171  calories  per 
hour.  Assuming  that  .similar  results  would  have  been  obtained  for 
c.  \V.  Miller,  it  can  he  computed  that  if  the  rider  remained  on  the 

wheel    twenty-three  hours  of    the  day,  the  heal   equivalent  of  external 
"I  .  s    im.j,,     \.,r    Officool  Experiment  Stations  Bui.  98. 


44 

muscular  work  would  be-  1,817  calories  per  day.  Similarly,  if  lie 
produced  471  calories  per  hour  in  riding,  the  total  heat  production 
for  the  day  would  be  10,833  calories.  This  is  the  maximum  workday 
of  the  six  days  that  Miller  rode.  R.  C.  Carpenter's  computations 
of  the  heat  equivalent  of  work  done,  however,  resulted  in  4,917 
calories  instead  of  1,817  calories,  as  found  as  a  result  of  the  experi- 
ments with  N.  B.  An  error  so  large  as  this  is  of  value  only  in  one 
way,  namely,  in  showing  the  utter  futility  of  attempting  to  compute 
energy  transformations  in  experiments  involving  so  many  complex 
factors,  such  as  tire,  wind,  and  chain  resistance,  as  are  found  in  ex- 
periments with  the  professional  bicycle  rider.. 

Assuming  that  the  work  done  during  the  six-day  race  is  comparable 
to  the  maximum  work  performed  by  N.  B.,  i.  e.,  112  calories  of 
external  muscular  work  per  hour,  and  assuming  that  the  riders  re- 
main on  the  wheel  twenty-three  hours  per  day,  the  maximum  heat 
equivalent  of  external  muscular  work  would  be  2,576  calories.  From 
the  degree  of  exhaustion  experienced  by  Mr.  Butler  on  the  four 
different  days  during  which  the  bicycle  was  ridden  at  1.25  amperes, 
it  is  highly  probable  that  this  degree  of  resistance  is  considerably 
greater  than  that  when  riding  a  track  during  a  six-day  race.  As 
has  been  pointed  out  above,  the  stimulus  of  competition,  the  pres- 
ence of  an  audience,  etc.,  were  lacking,  and  unquestionably  Mr. 
Butler  became  more  exhausted  in  these  tests  than  he  would  have 
been  under  conditions  in  which  there  was  greater  psychic  stimulation. 
It  is  more  than  probable  that  the  estimate  of  0.9  ampere  resistance 
was  very  close  to  the  resistance  actually  experienced  in  riding  during 
a  six- day  race. 

Irrespective  of  the  actual  amount  of  external  muscular  work  per- 
formed it  is  seen  that  the  results  with  all  these  riders  show  a  remark- 
able constancy  in  that  the  efficiency  is  very  close  to  21  per  cent,  and 
the  estimates  of  R.  C.  Carpenter,  although  admittedly  on  deficient 
basis,  are  scarcely  to  be  considered  even  as  approximations.  This 
emphasizes  again  the  great  difficulties  of  computing  the  results  of 
experiments  involving  factors  such  as  those  above  mentioned. 


THE  INFLUENCE  OF  MENTAL  WORK  ON  METABOLISM. 


EARLIER  INVESTIGATIONS. 

That  muscular  work  has  an  appreciable  effect  on  metabolism  was 
recognized  by  physiologists  at  a  very  early  date.  The  experiments 
of  Sanctorius0  early  in  the  seventeenth  century  show  an  attempt  to 
secure  accurate  knowledge  of  physiological  processes  and  the  effects 
of  muscular  work.  He  recognized  that  a  loss  of  body  weight  is  possi- 
ble even  without  appreciable  muscular  work,  and  designated  the  ma- 
terial which  was  lost  "  insensible  perspiration."  Observations  were 
commonly  made  by  early  investigators  of  the  increase  in  the  pulse 
and  respiration  rates,  the  appearance  of  sensible  perspiration,  and  the 
loss  of  weight  following  prolonged  muscular  effort.  Lavoisier  pos- 
sessed a  remarkably  clear  conception  of  the  quantitative  relations  of 
the  factors  of  metabolism,  as  is  evinced  by  the  fact  that  he  recorded 
a  large  number  of  observations  regarding  the  influence  of  muscular 
exertion  on  metabolism. 

Lavoisier  and  Seguin b  evidently  believed  that  mental  as  well  as 
muscular  exertion  might  influence  metabolism,  for  they  considered 
the  possibility  of  measuring  both  by  the  same  unit,  i.  e.,  the  degree 
of  oxidation,  and  doubtless  based  their  conception  upon  experimental 
evidence.  The  details  of  the  methods  employed  by  them  in  arriving 
ai  this  conclusion  are  unfortunately  lacking,  as  is  the  case  in  many 
other  researches  of  Lavoisier.  In  their  discussion,  the  muscular 
movements  involved  in  lifting  a  weight,  giving  a  lecture,  and  playing 
upon  a  musical  instrument  were  considered;  and  as  types  of  mental 
work  they  cited  the  writing  of  a  letter,  the  composition  of  music,  and 
the  mental  effort   of  a  philosopher's  reasoning. 

Although  of  little  absolute  scientific  value,  these  observations  of 
Lavoisier  and  his  coworker  are  of  interest  as  indicating  that  thus 
eaii\  in  the  history  of  experimental  science  investigators  were  at- 
tempting to  correlate  mental  and  physical  processes.  As  late  as  1  s 7 r> . 
Liebermeister c  sustained  Lavoisier's  vie\*  that  mental  processes  are 
comparable  with  muscular  movement.-,  ami  in  support  of  the  theory 
cited    an    incomplete   experiment    on    Professor   [mmermann    which 

"  De  liedicina  Btatica  Aphorisimi.     v  enice,  L614. 

6  m.ii  .  re   de  Lb  \  oi  net    ll    p.  697. 

•  Pathologic  und  Therapie  da  Fiebere,  L875,  p.  L96. 

I  i-v 


46 

implied  that  so  far  as  the  carbon  dioxid  excretion  is  concerned  the 
values  found  seemed  to  substantiate  Lavoisier's  view.  The  only 
factor  measured  was  carbon  dioxid,  and  Liebermeister  admits  that 
the  results  are  not  absolutely  convincing. 

Physiologists  for  a  long  time  attempted  to  establish  some  relation 
between  brain  and  nerve  activity  and  muscular  work.  When  a 
muscle  works  heat  is  developed,  and  in  the  attempt  to  show  the  rela- 
tion between  brain  and  nerve  and  muscles  many  experiments  were 
made  for  the  purpose  of  proving  that  heat  is  developed  in  a  nerve 
when  stimulated.  For  instance,  Claude  Bernard,"  using  a  thermo- 
electric needle  for  his  measurements,  reported  such  a  development 
of  heat. 

On  the  other  hand,  Heidenhain,6  Helmholtz,c  and  Rollestond  were 
unable  to  demonstrate  the  formation  of  heat  in  nerves. 

The  influence  of  muscular  activity  on  body  temperature  has  long 
been  known,  and  many  experiments  have  been  made  to  determine 
whether  mental  work  exercised  a  similar  influence  on  body  tempera- 
ture. John  Davye  made  a  large  number  of  sublingual  temperature 
observations  on  himself,  and  reports  that  during  the  evening  sus- 
tained mental  effort  due  to  reading  produced  a  slightly  higher  tem- 
perature than  was  normally  obtained  either  when  reading  merely 
for  amusement  or  when  engaged  in  the  mechanical  process  of 
copying. 

When  residing  in  the  Tropics  Davy-*"  reports  that  mental  exertion 
raised  the  body  temperature  1.1°  F. 

Rumpfs'  observed  that  when  he  was  reading  between  9  and  12  in 
the  evening  the  falling  of  the  temperature  curve  which  would  nor- 
mally be  expected  did  not  occur. 

Speck h  and  Gley*  also  observed  slight  increases  in  temperature 
as  a  result  of  mental  activity.  Thus  Speck  reports  that  on  three 
resting  days  his  body  temperature  was  35.7°,  35.7°,  and  35.8°  C, 
while  on  days  with  mental  activity  the  values  were  35.9°,  35.8°,  and 
36°  C,  an  increase  so  slight  that  he  was  inclined  to  attribute  it  wholly 
to  minor  differences  in  muscular  activity. 

Allbutt,  according  to  Pembrey/  records  that  a  long  series  of 
observations  failed  to  indicate  that  mental  effort  affected  body  tem- 

o  Vorlesungen  iiber  der  Thierische  Warme.     Trans,  by  Schuster,  1876,  p.  151.     Cited 
by  Speck,  Arch.  Expt.  Path.  u.  Pharmakol.,  15  (1881),  p.  87. 
b  Stud.  Physiol.  Inst.  Breslau,  4  (1868),  p.  250. 
c  Arch.  Anat.  Physiol,  u.  Wiss.  Med.,  1848,  p.  158. 
d  Jour.  Physiol.,  11  (1890),  p.  208. 
«  Phil.  Trans.,  1845,  p.  319. 
/Ibid.,  1850,  p.  443. 

<7Arch.  Gesam.  Physiol.,  33(1884),  p.  601. 
^Loc.  cit. 

*Compt.  Rend.  Soc.  Biol.  [Paris],  1884,  p.  265. 
3  Textbook  on  Physiology,  edited  by  E.  A.  Schafer,  New  York,  1898,  Vol.  I,  p.  808. 


47 

perature.  Judging  by  the  works  cited  above,  the  consensus  of 
opinion,  then,  is  that  but  little  influence,  if  any,  is  exerted  on  the 
temperature  of  the  body  as  a  whole  by  mental  activity. 

Aside  from  the  measurements  of  body  temperature  determined  in 
the  mouth  or  rectum,  many  observations  have  been  made  regarding 
the  regional  temperature  of  the  body,  and  more  especially  of  the 
head,  recorded  by  some  delicate  means  as  the  use  of  a  thermal  junc- 
tion. The  most  elaborate  investigation  of  this  character  with  which 
we  are  familiar  is  that  of  Lombard,0  who  made  an  exhaustive  series 
of  experiments  in  which  the  regional  temperatures  of  the  head  before, 
during,  and  after  excessive  mental  exercise  were  observed.  He  con- 
cluded that  mental  effort  results  in  a  distinct  rise  in  the  temperature 
of  the  head. 

A  profitable  line  of  investigation  seemed  to  be  found  when  a  study 
of  the  amount  of  blood  in  the  brain duringmental  work  was  attempted 
with  the  plethysmograph  and  balance  table,  but  Mosso  and  Gia- 
comiani,6  who  studied  the  question,  reported  that  each  movement 
of  the  body  as  well  as  mental  activity  produced  fluctuations  in  the 
volume  and  pulsation  of  the  brain.  So  it  is  difficult  to  determine 
how  much  of  the  effect  is  to  be  ascribed  solely  to  mental  work.  In 
working  on  the  same  line  of  investigation,  Frank0  found  that  mental 
work  caused  a  rise  in  the  pulse  curve  in  the  brain,  but  since  the 
respiration  was  similarly  altered  he  questions  whether  these  changes 
were  wholly  due  to  mental  activity.  Thanhofle-r''  also  reports  that 
mental  activity  influenced  the  pulse  rate,  while  Speck,6. on  the  con- 
trary, found  that  the  pulse  and  respiration  rates  when  the  mind 
was  actively  at  work  were  not  markedly  different  from  those  obtained 
when  he  was  half  asleep. 

Ii  is  a  well-known  fact  that  mental  condition  resulting  from  shock, 
fear  and  similar  psychological  phenomena  may  exert  a  marked 
influence  on  the  pulse  and  respiration  rates.  Where  such  fluctua- 
tion^ occur,  it  is  probable  that  the  results  are  not  the  same  as  those 
induced  by  muscular  activity,  and  it  seems  equally  clear  that  they 
are  of  nervous  rather  than  of  mental  origin. 

Many  observations  have  been  based  upon  the  assumption  that 
there  musl  be  disintegration  of  brain  substance  as  a  result  of  brain 
activity.  Theoretically,  if  mental  activity  is  accompanied  by 
increased  metabolism,  there  should  be  an  Increased  formation  of 
urea,  carbon  dioxid,  phosphoric  acid,  etc.  Among  the  earliest 
experiment-    reported    on    this   phase   of   the   question    are   those   of 

a  Experimental  Researches  on  the  Regional  Temperature  of  the  Head.     London, 

&Cent.  Med.  Wi--.,  1877,  p.  343. 
'  'k,  lo<\  cil.,  p.  91 . 
'Mr-  I,    Gesam.  Physiol.,  19  (1879),  p.  254. 
«  Loc.  < ■  it..,  p.  93. 


48 

Hammond,0  who  concluded  that  mental  effort  increased  the  quantity 
of  urine,  urea,  sodium  chlorid,  and  phosphoric  and  sulphuric  acid. 

In  reporting  a  series  of  experiments  made  on  himself,  however, 
Speck6  sharply  criticised  Hammond's  work,  and  stated  that  in  his 
opinion  there  is  no  noticeable  difference  in  the  urea  output,  and 
although  due  to  increased  mental  effort,  differences  in  the  amounts 
of  urine  are  found,  the  small  amounts  of  urine  are  always  of  a  high 
specific  gravity,  and  hence  there  is  no  retention  of  urea  and  similar 
products.  In  general,  Speck's  experiments  indicate  no  increase  in 
the  nitrogenous  output  as  the  result  of  mental  work. 

Oppenheim c  made  a  careful  study  of  the  urea  excretion  during  the 
day  and  night,  and  concluded  that  while  it  is  possible  so  to  regulate 
a  diet  as  to  produce  a  constant  urea  excretion,  it  is  obvious  that  the 
processes  taking  place  in  the  simple  nervous  system  are  not  so  regu- 
lated as  to  secure  equality  during  these  periods,  and  hence  it  is 
reasonable  to  assume  that  the  mental  processes  are  entirely  inde- 
pendent of  the  proteid  disintegration,  at  least  as  measured  by  the 
urea  excretion. 

Since  mental  activity  is  much  greater  during  the  day  than  during 
the  night,  at  least  according  to  all  notions  of  psychical  processes,  it 
was  believed  by  many  that  a  study  of  the  excretion  during  the  day 
and  night  would  reveal  the  influence  of  mental  activity.  As  a  matter 
of  fact,  it  has  been  found  that  somewhat  more  than  half  of  the  total 
nitrogen  eliminated  in  twenty-four  hours  is  excreted  in  the  urine  of 
the  day  period.  This  may  possibly  be  ascribed  to  the  fact  that  food 
is  ingested  only  during  the  day,  though  recent  experiments^  have 
shown  that  about  56  per  cent  of  the  total  nitrogen  in  the  urine 
voided  by  a  fasting  man  appears  in  the  urine  collected  between 
7  a.  m.  and  7  p.  m. 

Schenk e  found  that  loss  of  sleep  did  not  influence  noticeably  the 
nitrogenous  excretion. 

Sherman  f  in  studying  the  effect  of  the  loss  of  sleep  on  nitrogenous 
metabolism  reports  that  the  influence  on  the  nitrogen  output  was 
very  slight  and  did  not  appear  until  the  third  day. 

All  of  the  earlier  work  on  the  effects  of  mental  effort  on  the  chemical 
transformations  was  confined  to  the  examination  of  the  urine  for  two 
reasons:  (1)  The  urine  was  easily  collected  and  (2)  the  determina- 
tions of  nitrogen,  phosphorus,  and  chlorin  in  urine  could  be  easily 
made.     There  was  also  a  notion  commonly  held  that  mental  activity 

»Amer.  Jour.  Med.  S'ci.,  1856,  Apr.,  p.  335. 

&Loc.  cit.,  p.  97. 

cArch.  Gesam.  Physiol.,  23  (1880),  p.  455. 

d Carnegie  Inst.  Washington  Pub.  77. 

eArch.  Expt.  Path.  u.  Pharmakol.,  2  (1874),  p.  21. 

/U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  121. 


49 

was  in  some  special  manner  associated  with  the  transformation  of 
the  phosphorus-containing  material  of  the  brain,  and  so  many  of  the 
earlier  investigators  studied  the  phosphorus  output  also. 

B£oslef,°  for  example,  found  more  phosphorus  in  the  urine  passed 
during  the  evening  than  in  that  passed  during  the  day,  and  con- 
sidered it  to  be  due  to  more  active  brain  work.  Speck,6  however 
criticising  the  character  of  Mosler's  work,  showed  that  the  results 
of  his  experiments  do  not  indicate  that  an  increased  phosphorus 
elimination  occurs  during  the  evening. 

During  the  long  fasting  experiment  with  Succi  as  a  subject,  Luci- 
ani' observed  that  mental  work  such  as  was  involved  in  conversing 
and  visiting  with  friends  did  not  result  in  an  increase  in  the  nitroge- 
nous excretion.  On  the  other  hand,  as  a  result  of  the  examination 
of  the  renal  excretion  of  phosphorus,  Luciani  was  fully  convinced  of 
the  importance  of  this  element  as  an  index  of  metabolism  resulting 
from  mental  processes.  In  some  experiments  on  himself  made  in 
connection  with  Agostini,  a  quantitative  analysis  of  the  urine  was 
made  during  two  afternoon  hours  from  1.30  to  3.30.  These  were 
made  on  days  when  no  lectures  were  held  and  on  a  day  when  they 
met  their  students  and  a  lecture  was  given.  Care  was  taken  that 
the  same  quantities  of  food  and  drink  were  consumed  on  all  experi- 
mental days  and  that  the  food  was  eaten  at  the  same  time  each  day. 
The  results  of  these  investigations,  which  Luciani  states  should  be 
amplified,  agree  fully  with  those  on  Succi,  showing  that  mental  effort 
decreases  the  phosphorus  content  of  the  urine  in  so  far  as  its  relation 
to  nitrogen  is  concerned.  Luciani  also  cites,  in  confirmation  of  his 
view-,  work  by  Mendel,'  who  reports  data  wrhich  led  him  to  conclude 
thai  the  phosphoric  acid  of  urine  when  compared  to  the  sum  of  the 
total  solids  is  considerably  greater  in  the  night  urine  than  in  that  from 
the  day.  Further,  he  slates  that  in  chronic  mental  diseases  the 
daily  elimination  of  phosphoric  acid  in  proportion  to  the  total  solids, 
as  well  as  in  absolute  amount,  is  -mailer  than  that  of  healthy  persons 
under  the  same  dietetic  conditions,  and  that  maniacs  and  excitable 
individuals  show  an  absolute  decrease  in  the  amount  of  phosphoric 
acid  in  the  urine.  On  the  other  hand,  he  noted  an  increase  in  this 
ratio  as  a  result  of  apoplectic  and  epileptic  attacks. 

Bockerd  in  studying  the  relative  amounts  of  phosphates  in  urine 
found  there  was  a  very  distinct  diminution  of  the  alkaline  phos- 
phates during  the  night,  and  Mairet'  found  that  during  sleep  both 
the  alkaline  and  earthy  phosphates  are  diminished. 

"  [naug  3,  p.  12. 

6  Loc,  -ic,  p.  LOO. 

■  Dai  Eungern.     Leipzig,  L890,  p.  L60. 
&  cited  by  speck,  loc.  cit.,  p.  I L5. 
•  I  ompt.  Rend.  Soc.  Biol.  [Parol,  L884,  p.  285, 
70076    Bull.  ZOfi    09     -4 


50 

In  judging  of  the  value  of  experiments  on  phosphorus  excretion 
as  an  index  of  metabolism  in  the  brain,  it  is  necessary  to  take  into 
consideration  the  fact  that,  aside  from  the  metabolism  of  nucleo- 
proteids  in  the  body,  there  is  a  very  large  store  of  phosphatic  material 
in  the  bones  which  is  unquestionably  drawn  upon  and,  indeed,  with 
considerable  rapidity  under  certain  conditions.  Thus  a  large  number 
of  fasting  experiments  have  shown  that  in  certain  instances  at  least 
the  ratio  of  the  nitrogen  excreted  to  the  phosphorus  excreted 
implies  strongly  that  there  was  a  draft  upon  the  phosphatic  material 
of  the  bones.  Obviously,  since  there  is  such  a  reservoir  of  phos- 
phorus in  the  body,  slight  changes  in  the  excretion  from  hour  to  hour 
or  day  to  day  can  not  of  themselves  be  taken  as  an  index  of  the 
measure  of  nucleo-proteid  katabolism. 

The  methods  of  studying  phosphorus  metabolism  have  not  under- 
gone material  changes  in  recent  years,  being  based  upon  titration 
with  uranium  salts,  and  the  earlier  investigations  are  comparable  with 
recent  results.  It  has,  however,  recently  been  proven  that  there  is 
very  little,  if  any,  organic  phosphorus  in  the  urine,  and  this  is  an 
important  consideration  in  using  this  element  as  an  index  of  body 
change  and  indicates  that  to  be  of  value  experiments  should  in- 
clude the  kind  and  amount  of  phosphorus  compounds  rather  than 
total  phosphorus. 

In  all  probability  the  sulphur  output  is  a  much  more  accurate  index 
of  protein  katabolism  than  is  the  phosphorus  output,  and  there  has 
been  in  recent  years  a  marked  change  in  the  interpretation  of  the 
results  of  analyses  of  urine  in  which  sulphur  was  determined  and  an 
increasing  belief  in  the  importance  of  determining  the  compounds  in 
which  the  sulphur  is  excreted.  Originally  investigators  confined 
themselves  to  the  determination  of  the  preformed  sulphates. 

Baumanna  pointed  out  the  importance  and  relationship  of  the 
ethereal  sulphates,  and  in  more  recent  years  the  significance  of  the 
so-called  "neutral"  sulphur  has  become  recognized.  At  present, 
then,  our  knowledge  of  the  sulphur  output  in  the  urine  is  decidedly 
unsatisfactory,  and  in  view  of  this  fact  it  is  questionable  whether  the 
determinations  which  have  been  reported  throw  any  definite  light 
on  the  metabolism  of  protein  under  conditions  of  severe  mental 
activity. 

Of  earlier  investigators  Smith  h  observed  that  the  volume  of  respira- 
tion during  sleep  was  considerably  less  than  that  during  work,  and  as  a 
few  years  later  Scharling  found  an  increased  heat  production  during 
the  waking  hours  over  sleep  it  was  argued  that  the  mental  activity 
of  the  day,  in  part  at  least,  accounted  for  the  increased  metabolism. 
Liebermeisterc  also    found  a  decreased    carbon    dioxid    production 

a  Arch.  Gesam.  Physiol.,  13  (1876),  p.  300. 

ft  Phil.  Trans.  London,  149  (1859),  pt.  2,  p.  681. 

cHandbuch  der  Pathologie  und  Therapie  des  Fiebers,  p.  189. 


51 


during  the  sleeping  hours.  But  the  more  careful  experiments  of 
Johansson"  have  shown  that  under  conditions  in  which  all  extra- 
neous muscular  activity  is  eliminated  and  the  subject  secures  the 
greatest  possible  muscular  repose  the  carbon  dioxid  production  of 
the  resting  man  is  essentially  the  same  whether  awake  or  asleep. 

Speck6  used  his  respiration  apparatus  for  studying  the  problem 
of  the  influence  of  mental  work  on  metabolism.  The  mental  work 
consisted  in  reading  a  scientific  book,  in  writing  up  the  results  of 
experiments,  and  in  making  mathematical  calculations.  Experi- 
ments were  also  made  with  another  subject  who  during  the  mental 
work  period  translated  Latin  and  Greek.  In  all,  fifty-two  experi- 
ments were  carried  on,  in  which  the  ventilation  of  the  lungs,  the  car- 
bon dioxid  produced  and  oxygen  absorbed,  as  well  as  the  number  of 
respirations  per  minute  and  the  depth  of  each  respiration,  were  deter- 
mined. The  experiments  lasted  from  eight  to  seventeen  minutes. 
Speck  concludes  from  the  results  of  all  these  experiments  that  mental 
activity  exerts  no  influence  on  the  general  metabolism,  and  that  the 
molecular  processes  in  the  brain  are  either  nonoxidative  or  their 
effects  are  so  small  that  the  experimental  methods  followed  are  not 
sufficiently  delicate  to  measure  them. 

In  a  series  of  experiments  made  in  cooperation  with  the  United 
States  Department  of  Agriculture  and  reported  by  Atwater,  Woods, 
and  Benedict  in  1899/  the  attempt  was  made  to  study  the  effect  of 
mental  effort  with  the  aid  of  the  respiration  calorimeter,  which  was 
designed  in  connection  with  the  nutrition  investigations  of  this 
Department.  The  special  feature  which  permitted  the  measurement 
of  the  income  and  outgo  of  energy  had  not  yet  been  completed,  so 
the  energy  balance  could  not  be  taken  into  account,  and  the  work 
i-  comparable  in  character  to  that  reported  by  Pettenkofer  and  Voit, 
in  which  their  respiration  apparatus  was  used.  The  subject  of  the 
experiments  was  a  healthy  young  man,  assistant  in  physics  in  Wes- 
leyiiii  1  'Diversity.  During  three  days  of  the  experiments  he  remained 
very  quiei  and  endeavored  to  approximate  a  "vegetative"  condi- 
tion. On  the  next  three  days  he  spent  eight  hours  per  day  studying 
i)  German  treatise  <>n  physics  and  making  computations  connected 
with  experiments  with  the  respiration  apparatus.  The  average 
nitrogen  and  carbon  output  per  twenty-four  hours  are  given  in  (he 
following  table: 

Average  daily  output  of  nitrogen  and  carbon  in  rest  and  mental  work. 


Period. 

Duration. 

Nitrogen. 

Carbon. 

3 

ia  i 

vi.:, 

(I 111  III X. 

341.0 

248.  I 

.  ...                         

ind.  Arch.  Physiol.,  -     L898     ; 
'<Ar.li.  Expt.  Path.  ii.  Pharmakol.,  L5  (1881),  p.  L28.    See  also  Physiologic  dea 

tilischen  Athmens.  Leipzig,  1892,  |>.  204. 
cf.  S.  Dept.  Agr. ,  Office  of  Experiment  Bull.  44, 


52 

It  is  evident,  therefore,  that  in  this  experiment  the  mental  effort 
resulted  in  no  marked  or  noticeable  alteration  in  the  general  metab- 
olism, for  while  there  was  a  slightly  higher  output  o,f  nitrogen 
during  the  mental  work  period,  there  was  a  somewhat  smaller  output 
of  carbon.  . 

Of  interest  in  this  connection  are  the  experiments  reported  by 
Obici,a  who  notes  that  the  mental  effort  accompanying  mathe- 
matical calculations  resulted  in  an  increased  respiration  rate  and 
a  deeper  inspiration,  and  thus  the  lungs  are  more  completely  venti- 
lated than  usual.  When  the  subject  is  mentally  exhausted,  the  rate 
and  volume  of  respiration  decrease  markedly. 

Not  only  have  attempts  been  made  to  study  the  effect  of  mental 
strain  by  the  methods  above  referred  to,  but  the  natural  supposi- 
tion that  the  fatigue  resulting  from  muscular  work  was  properly 
comparable  with  that  resulting  from  mental  effort  has  been  the 
basis  of  another  line  of  investigation  in  which  an  ergograph  of 
special  construction  has  been  used  to  measure  the  effect  on  fatigue 
of  a  variety  of  conditions.  The  well-known  work  of  Mosso  and 
Maggiora  proved  conclusively  that  mental  exertion  produces  not 
only  psychical  weariness,  but  results  also  in  a  distinct  loss  of  muscle 
power.  Thus  in  a  series  of  experiments  on  Doctor  Maggiora,  Mosso6 
showed  by  his  ergograph  that  the  onset  of  fatigue  was  very  much 
more  rapid  after  a  severe  mental  strain,  such  as  that  accompanying 
the  questioning  of  candidates  in  an  examination.  Furthermore 
the  return  to  the  normal  condition  was  delayed  at  least  two  hours 
after  the  mental  effort  and  probably  considerably  longer.  Thus 
scientific  research  verifies  the  popular  conception  that  mental  exer- 
tion results  in  a  marked  lowering  of  the  muscular  power. 

MEASUREMENTS  OF  MENTAL  WORK. 

While  it  is  possible  by  means  of  the  ergograph  to  show  definitely 
the  influence  of  intellectual  activity  on  muscular  power  and  the 
onset  of  fatigue,  the  problem  of  demonstrating  the  influence  of  intel- 
lectual activity  upon  any  of  the  ordinary  processes  of  metabolism 
is  extremely  complex,  since  it  is  evidently  unscientific  to  rely  on 
personal  impressions  as  to  degree  of  fatigue  and  exhaustion.  For 
a  satisfactory  study  of  the  problem  it  is  necessary,  in  order  to  obtain 
conclusive  results,  to  measure  first  the  degree  of  mental  activity  and 
second  to  measure  the  products  of  metabolism  with  such  a  degree 
of  refinement  as  to  show  the  influence  of  a  factor  which  must  be 
small  in  comparison  with  the  better  understood  factors — muscular 
work,  for  instance — which  influence  anabolic  and  katabolic  body 
processes. 

oRiv.  Sper.  Freniatria,  27  (1901),  Dec;  abst.  in  Jahresber.  Tier-Chem. ,  32  (1902), 
p.  621. 

b  La  Fatigue  Intellectuelle  et  Physique.     Paris,  1900,  p.  152, 


53 

The  ordinary  methods  of  the  psychologist  for  studying  the  intensity 
and  degree  of  mental  exertion  depend  upon  comparative  measure- 
ments of  the  relative  rapidity  with  which  columns  of  figures  can  be 
added,  or  words  or  passages  memorized,  or  some  similar  test, 

An  attempt  to  measure  mental  activity  through  muscular  work 
was  also  made  in  Loeb's  laboratory  by  Jeanette  C.  Welch/  in  con- 
nection with  a  series  of  experiments  to  study  the  so-called  "con- 
stant of  attention,"  using  a  dynamograph  devised  by  Loeb. 

Btit  such  tests  in  general  occupy  but  a  short  space  of  time,  and 
measurements  of  metabolic  activity  are  as  a  rule  unreliable  for 
such  short  periods.  Consequently  the  usual  tests  of  the  psycholo- 
gist can  not  well  be  applied  in  studies  of  the  effect  of  mental  work 
on  metabolism,  and  it  becomes  necessary  to  use  some  method  of 
measurement  which  will  cover  a  considerable  time. 

From  the  results  of  previous  investigations,  which  have  been 
summarized  in  the  foregoing  pages,  it  is  clear  that  the  influence 
of  mental  effort  on  metabolism  is  in  all  probability  not  great,  as 
compared  witli  other  factors  which  affect  it,  and  hence  in- planning 
a  study  of  this  question  it  is  desirable  to  employ  some  form  of  mental 
effort  that  will  be  at  once  long  continued  and  intense,  and  thus 
attempt  to  exert  the  maximum  effect  on  metabolism  and  to  use  a 
method  which  is  accurate  and  suitable  for  measuring  small  changes 
in  metabolism.  Theoretically,  intense  application  to  the  study&of 
certain  mathematical  problems  might  at  first  sight  appear  best 
adapted  for  long-continued  mental  effort,  or  some  similar  task  which 
involves  concentration  of  mental  powers  and  is  considered  difficult 
by  the  subject, 

In  the  experiments  reported  beyond,  the  subjects,  during  the  mental 
work  period,  were  engaged  in  answering  the  questions  in  written 
examinations  in  a  number  of  different  university  subjects,  and  the 
work  may  fairly  be  regarded  as  at  least  reasonably  exacting  for  the 
average  student. 

METHODS  OF  MEASURING  RESULTS  OF  MENTAL  EFFORT. 

The  previous  studies  of  Mosso,  and  of  psychologists  such  as  Krae- 
pelin,  have  shown  the  results  of  menial  effort  in  diminishing  muscular 
strength  as  measured  by  (he  ergograph  and  the  retarding  effect  of 
mental  activity  as  shown  by  a  lengthened  reaction  time.  But  for 
reasons  already  stated  such  experiments  do  nol  seem  adequate,  and 
it  seems  certain  thai  a  study  of  the  effed  of  mental  activity  on 
metabolism  is  of  especial  importance  and  likely  to  give  results  of 
value.  Metabolic  transformations  can  be  measured  in  two  ways: 
(1  By  the  results  of  chemical  changes,  oxidative  processes,  cleavage, 
changes  in  the  body,  etc.;  and  (2)  by  the  energy  transformations 
milting  from  the  katabolic  proce 

"AiiM'f.  .1  ,    283. 


54 

CHEMICAL  TRANSFORMATIONS. 

For  purposes  of  study  we  can  consider  the  body  as  composed 
chiefly  of  the  three  chemical  compounds,  protein,  fat,  and  carbohy- 
drates. A  considerable  number  of  other  chemical  compounds  are 
also  present,  but  in  much  smaller  amounts.  It  has  commonly  been 
supposed  that  the  best  index  of  protein  katabolism  is  the  excretion 
of  nitrogen  in  the  urine,  although  in  recent  years  the  great  significance 
of  the  partition  of  the  nitrogen  excreted  in  the  urine  has  become  more 
apparent.  A  study  of  the  transformations  of  protein  may  be  made 
with  considerable  accuracy  and  with  no  especially  complex  appa- 
ratus by  collecting  the  24-hour  quantity  of  urine  and  subjecting  it 
to  chemical  analysis.  But  the  transformations  of  fat  and  carbohy- 
drates can  be  studied  only  by  an  apparatus  permitting  an  accurate 
measurement  of  the  respiratory  gases,  and  therefore  it  is  necessary 
to  utilize  a  much  more  complex  apparatus,  such  as  the  respiratory 
apparatus  of  Zuntz-Geppert  or  the  larger  respiration  chambers  of  the 
Pettenkofer  and  Voit  type. 

From  the  well-known  functions  of  the  brain  it  is  logical  to  suppose 
that  mental  effort  would  result  in  increased  chemical  transformations 
in  the  brain  substance  itself.  It  has  been  the  common  belief  that 
mental  processes  involve  not  only  the  disintegration  of  ordinary 
flesh  protein,  but  also  of  the  nucleo-proteins,  lecithin,  kephalin,  etc., 
of  the  brain.  These  compounds  are  especially  rich  in  phosphorus, 
and  hence  much  significance  has  been  laid  upon  the  elimination  of 
phosphorus  in  the  urine.  The  experimental  evidence  thus  far  pre- 
sented, however,  fails  to  establish  any  relation  between  mental 
activity  and  phosphorus  metabolism. 

Protein  contains  sulphur,  and  this  element  also  has  been  studied 
as  an  index  of  protein  katabolism,  and  there  are  reasons  for  believ- 
ing that  such  a  method  is  especially  desirable  under  suitable  con- 
ditions. 

A  critical  study  of  the  nitrogen,  sulphur,  and  phosphorus  output 
shows  that  the  amount  excreted  is  a  result  of  a  series  of  very  complex 
changes.  With  regard  to  the  element  nitrogen,  for  example,  the 
work  of  Folin  has  shown  that  variations  in  diet  produce  markedly 
different  nitrogenous  excretions.  In  fact,  the  differences  are  so 
great  as  to  lead  Folin  to  contend  that  there  are  two  kinds  of  protein 
katabolism,  the  so-called  endogenous  and  exogenous.  All  of  the 
evidence  indicates  a  much  more  complex  katabolism  than  the  sim- 
ple urea  determinations  of  the  earlier  writers  would  imply,  and  while 
it  is  very  evident  that  the  total  nitrogen  output  as  determined  by 
the  Kjeldahl  method  is  a  much  better  index  of  protein  katabolism 
than  was  the  total  urea  determination  as  made  by  the  faulty  and 
defective  Liebig  method,  yet  in  any  study  in  which  the  influence 
of  a  subtle  factor  such  as  mental  effort  is  to  be  studied,  a  much  more 
satisfactory  and  delicate  measure  of  metabolism  must  be  used. 


55 

Furthermore,  while  the  total  nitrogen  output  is  of  value  in  indica- 
ting the  loss  of  this  chemical  element  to  the  body,  it  is  of  little  value 
for  the  study  of  the  minor  factors  influencing  metabolism  and  espe- 
cially the  intermediary  metabolism.  A  careful  study,  by  modern 
methods,  of  the  purin  metabolism  may  ultimately  throw  some  light 
on  the  disintegration  products  of  protein  katabolism  as  affected  b}T 
mental  exertion.  In  connection  with  the  series  of  mental  tests  here 
reported  it  was  impracticable  to  make  such  a  study,  as  it  would 
involve  the  consumption  of  a  carefully  selected  and  constant  diet 
which  should  be  adhered  to  for  a  sufficient  period  to  secure  a  constant 
purin  output,  and  under  the  experimental  conditions  this  was  not 
possible. 

It  is  recognized  by  all  students  of  metabolism  that  the  total 
metabolism  can  best  be  studied  by  measuring  the  respiratory  gases. 
Fortunately,  by  means  of  the  respiration  calorimeter  in  the  chemical 
Laboratory  of  Wesleyan  University,  this  method  of  study  was  pos- 
sible. The  apparatus  permits  the  determination  of  the  water  vapo- 
rized from  the  lungs  and  skin,  the  carbon  dioxid  output,  and  the 
oxygen  intake.  The  periods  during  winch  the  subjects  were  studied 
in  the  respiration  calorimeter  covered  three  hours  and,  since  check 
tests  had  shown  the  apparatus  to  be  extremely  accurate  for  experi- 
ments of  this  duration,  it  is  believed  that  the  recorded  measurements 
of  water  output  and  carbon  dioxid  elimination  are  as  accurate  as 
could  be  desired. 

Unfortunately,  owing  to  the  rapidity  with  which  the  tests  had  to  be 
made,  the  large  number  carried  on,  and  similar  causes,  the  oxygen 
determinations  in  some  of  the  experiments  were  unsatisfactory, 
though  in  the  majority  of  cases  they  are  regarded  as  trustworthy. 
Although  the  effects  of  various  well-known  factors  on  protein  metab- 
olism are,  in  all  cases,  slow  in  manifesting  themselves,  it  is  fortunate 
that  the  factors  affecting  general  metabolism  are  almost  invariably 
characterized  by  marked  changes  in  the  respiratory  gases,  and  indeed 
almost  immediately  after  the  factor  has  begun  to  influence  the  trans- 
formation. Perhaps  the  most  striking  evidence  of  this  is  offered  by 
tin-  experiments  of  BoweE  and  Iligley,®  who  noted  that  intense, 
muscular  work  resulted  in  a  noticeable  increase  in  the  carbon  dioxid 
Output    within    twenty    seconds    after    the    effort     began.      While    the 

e.\t  rente  sensitiveness  of  the  respiratory  gases  to  t  he  factors  influencing 

metabolism  i>  on  the  one  hand  of  decided  advantage  in  studying  the 

influence  of  a  factor  admittedly  so  subtle  as  is  that  of  mental  exertion, 
yet  t  hi- extreme  sensitiveness  also  has  a  certain  disadvantage,  for  it  is 
likewise  susceptible  to  the  influence  of  the  slightest  muscular  activity, 
the  work  of  digestion,  etc.  Hence  it  is  of  vital  importance  that  all 
condition-  other  than  the  one  studied  be  constant  in  all  experiments 
on  the  influence  of  mental  work.     The  most  marked  influence  on  the 


"Am.r.  Jour.  Plfj  iol.,  I  !    i'"»i     p  3J  I- 


56 

respiratory  exchange  is  produced  by  muscular  activity,  and  for  this 
reason  especial  efforts  were  made  in  our  experiments  to  control  this 
factor,  and  probably  the  routine  followed  resulted  in  a  reasonably 
close  approximation  to  constancy,  but  the  diet,  the  degree  of  nervous- 
ness, sleepiness,  etc.,  of  the  different  subjects  could  not  be  con- 
trolled. It  is  furthermore  highly  probable  that  during  the  periods 
when  the  examinations  were  made  the  subjects  were  influenced  more 
by  irregular  hours  of  sleep,  nervousness,  and  possibly  in  some  cases 
by  irregularity  of  meals,  than  during  any  other  time  of  the  year. 
These  facts  are  mentioned  to  make  it  clear  that  it  is  recognized  that 
the  conditions  for  conducting  these  experiments  were  by  no  means 
ideal,  yet  they  were  as  favorable  perhaps  as  could  be  expected  and  all 
possible  care  was  taken  to  avoid  error.  The  data  are  given  in  detail 
and  show  the  actual  conditions  under  which  the  experiments  were 
conducted. 

MEASUREMENT  OF  HEAT. 

The  importance  of  a  measurement  of  heat  production  in  studying 
the  possible  influence  of  mental  effort  oh  metabolism  may  be  realized 
when  the  popular  notion  is  recalled  that  during  a  severe  mental  test, 
such  as  an  examination  in  some  difficult  subject,  individuals  have  a 
distinct  feeling  that  they  are  working  hard  and  perspire  freely  at 
times,  and  that  consequently  it  is  conceivable  that  extreme  mental 
effort  might  affect  the  heat  output.  The  measurement  of  heat 
radiated  from  the  body  has  not  commonly  been  reported  in  experi- 
ments on  man,  but  the  respiration  apparatus  here  used  was  so  com- 
bined with  calorimetric  devices  as  to  permit  the  measurement  of  the 
heat  production  and  respiratory  products  simultaneously.  While  the 
respiratory  exchange  and  heat  production  apparently  go  hand  in 
hand,  strictly  speaking,  this  is  not  always  true,  for  when  fat  is  burned 
much  more  heat  is  eliminated  per  gram  of  carbon  dioxid  liberated 
than  when  carbohydrates  are  burned.  This  fact  is  of  importance  in 
interpreting  the  results  of  the  experiments,  especially  those  in  which 
diets  of  different  nature  are  used,  by  devising  a  routine  of  muscular 
movements  which  each  subject  followed,  and  determining  the 
respiratory  exchange  alone  might  not  show  the  influence  of  mental 
exertion,  since  such  influence  might  be  masked  by  the  influence  of  the 
variations  in  the  diet.  On  the  other  hand,  the  heat  production,  while 
unquestionably  affected  somewhat  by  the  ingestion  and  assimilation 
of  food,  is  by  no  means  as  markedly  influenced  as  is  the  respiratory 
exchange. 

A  measure  of  the  heat  elimination  alone  does  not  give  a  true  index 
of  the  heat  production,  for  it  may  happen  in  some  instances  that  the 
body  temperature  is  lowered  noticeably  during  an  experimental 
period,  thus  indicating  a  loss  of  heat  from  the  body  which  was  not 


57 

necessarily  produced  during  the  period.  Conversely,  an  increase  in 
the  body  temperature  may  result  in  a  storage  of  heat  in  the  body  which 
is  not  measured  by  the  calorimeter,  though,  strictly  speaking,  it  was 
produced  during  the  experimental  period.  In  accurate  experiments, 
therefore,  it  is  necessary  to  take  account  not  only  of  the  heat  elimi- 
nation, but  also  of  the  heat  production.  This  involves  a  careful 
measurement  of  body  temperature  and  body  weight.  The  loss  of 
weight  of  material  during  a  period  indicates  the  cooling  of  a  certain 
mass  of  material  from  the  temperature  of  the  body  to  that  of  the 
calorimeter,  but  does  not  imply  an  actual  heat  production  during  the 
period  of  this  amount  of  heat.  For  measuring  body  temperature  it 
has  been  the  custom  for  many  years  in  the  metabolism  experiments 
conducted  with  the  respiration  calorimeter  to  use  a  delicate  electrical 
resistance  thermometer  which  can  be  inserted  in  the  rectum  and  per- 
mits the  making  of  records  of  the  body  temperature  deep  in  the  trunk. 
It  was  found  impracticable  to  employ  this  method  in  the  experiments 
here  reported,  and  consequently  the  subjects  at  stated  periods  of 
the  day  took  their  sublingual  temperature  with  a  mercurial  clinical 
maximum  thermometer,  and  these  resulting  records  of  temperature 
changes  were  used  in  computing  the  heat  production. 

GENERAL  PLAN  OF  THE  EXPERIMENTS. 

In  the  experiments  here  reported  the  plan  was  adopted  of  comparing 
the  general  metabolism,  including  the  heat  production,  during  a 
period  of  intense  mental  effort  with  the  general  metabolism  and  heat 
production  during  a  period  of  comparative  mental  rest.  The  respira- 
tion calorimeter  at  Wesleyan  University  was  used  for  obtaining  the 
measurement  of  carbon  dioxid,  water,  oxygen,  and  heat.  Inciden- 
tally, observations  regarding  body  temperature,  pulse  rate,  loss  in 
body  weight,  and  personal  impressions  were  likewise  recorded  in  all 
the  experiments.  No  analyses  of  the  urine  were  made,  but  it  is 
believed  that  the  determination  of  the  respiratory  products  and  the 
beat  production  sufficed  for  the  purpose  in  hand  and  furnished  as 
accurate  a  measure  of  metabolism  as  it  was  possible  to  obtain  under 
the  circumstances. 

The  period  of  mental  activity  involved  was  in  all  cases  the  three 
hour-  devoted  to  taking  the  regular  collegiate  midyear  examinations 
in  >ome  special  subject.  During  these  examinations  the  men  are 
subjected  to  a  two  to  three  hour  test  of  their  mental  powers,  and 
there  is,  as  a  rule,  a  great  .stimulus  to  concentrated  and  continued 
menial  effort.  There  is  presumably  more  uniformity  m  the  mental 
condition  of  a  number  of  students  under  examination  than  is  readily 
obtainable  in  any  series  of  artificial  and  more  or  less  unfamiliar  con- 
ditions as  could  be  readily  obtained  by  other  means.     A  Large  num.- 


58 

ber  of  men  (twenty-two)  was  included  in  this  study,  with  the  idea  of 
eliminating  the  personal  equation  in  so  far  as  possible  and  of  includ- 
ing tests  of  memory  in  which  originality  should  play  an  important 
role. 

The  periods  in  which  the  effects  of  mental  work  were  studied  were 
followed  after  an  interval  by  control  tests  in  which  the  mental  work 
was  of  the  sort  which  is  generally  considered  light,  the  subjects  being 
engaged  in  copying  something  in  which  they  were  not  especially  inter- 
ested or  in  reading  something  demanding  no  concentrated  mental 
effort. 

The  respiration  calorimeter,  as  has  been  explained  in  earlier  pub- 
lications of  this  series,0  is  equipped  with  a  chair,  table,  and  other 
conveniences  and  is  lighted  by  a  window  in  the  front.  As  regards 
comfort,  indeed,  the  subjects  were  under  no  abnormal  conditions. 
They  were,  to  all  intents  and  purposes,  simply  taking  an  examination 
of  their  college  in  a  small  room  where  they  could  give  their  whole 
thought  to  it. 

Each  subject  entered  the  calorimeter  chamber  a  little  over  an  hour 
before  the  experiment  began.  Previous  to  this  he  had  been  given  as 
much  water  as  he  wished,  and  had  been  requested  to  defecate  if  pos- 
sible, in  order  to  avoid  defecation  during  the  examination  period. 
Aside  from  the  permanent  fixtures  inside  the  chamber,  such  as  the 
shelves  and  telephone,  a  table  of  convenient  height  and  a  comfortable 
wooden  armchair  were  provided,  so  as  to  enable  the  subjects  to  take 
their  examinations  under  favorable  conditions  as  regards  physical 
comfort.  The  table  and  chair  were  so  placed  that  the  light  from  the 
window  entered  at  the  left.  A  previously  weighed  bottle  containing 
drinking  water  was  placed  in  the  chamber,  as  were  also  two  bottles 
for  the  collection  of  urine. 

The  subject,  wearing  his  ordinary  clothing,  entered  the  chamber 
and  after  being  weighed  while  seated  in  the  chair  which  was  swung 
from  a  balance  scale  outside  the  chamber,  assumed  a  comfortable 
position  and  read  or  wrote  until  time  for  the  examination  to  begin. 

A  few  moments  before  the  experimental  period  began  determina- 
tions of  the  amounts  of  carbon  dioxid  and  residual  water  vapor  in  the 
air  of  the  calorimeter  system  were  made,  and  five  minutes  before  the 
experimental  period  the  subject  was  asked  to  place  a  clinical  ther- 
mometer in  the  mouth  under  the  tongue.  Immediately  after  the 
experimental  period  began  the  subject  went  to  the  opening  of  the 
calorimeter  through  which  food  and  minor  articles  are  passed,  placed 
the  clinical  thermometer  in  it,  and  removed  therefrom  the  examina- 
tion paper.  He  then  resumed  his  chair  and  immediately  began  to 
write  the  answers  to  the  examination  questions. 

«U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Buls.  63,  109,  136,  175. 


59 

PULSE  RATE. 

At  the  time  these  experiments  were  made  a  pneumograph  for 
obtaining  the  pulse  rale  was  not  in  use  by  us,  and  so  the  subjects 
were  instructed  to  count  the  radial  pulse  in  the  left  arm,  using  a  stop 
watch  and  recording  the  number  of  beats  and  the  seconds  in  fractions. 
Subsequently  all  the  observations  were  computed  on  the  basis  of 
the  number  of  beats  per  minute.  The  pulse  rate  was  taken  several 
times  during  the  three-hour  period,  although  no  direct  instructions 
regarding  the  times  for  taking  the  pulse  rate  were  given. 

GENERAL  IMPRESSIONS. 

In  order  to  obtain  as  accurately  as  possible  an  estimate  of  the 
mental  condition  of  the  subjects,  they  were  requested  to  note  down 
from  time  to  time  their  personal  impressions  regarding  comfort  or 
discomfort,  ventilation,  temperature,  noise  or  distraction,  and  light. 

CHARACTER  OF  FOOD  PRECEDING  THE  EXPERIMENTS. 

Most  of  these  experiments  were  made  within  two  hours  after  a 
meal  was  taken,  and  hence  it  seemed  desirable  to  have  a  record, 
even  though  it  be  but  approximate,  of  the  kind  and  amount  of  food 
eaten  at  the  preceding  meals  and  the  time  the  meals  were  taken. 
From  the  well-known  effect  of  the  ingestion  of  food  on  the  respira- 
tory quotient  the  data  thus  secured  are  of  much  importance  in  inter- 
preting the  respiratory  exchange. 

At  the  conclusion  of  the  experiment  the  body  temperature  and 
the  body  weight  were  again  taken,  alter  which  the  subject  left  the 
chamber. 

SUBJECTS  OF  THE  EXPERIMENTS. 

The  subjects  of  these  experiments  were  all  healthy  young  men, 
ranging  from  17  to  29  years  of  age,  students  in  Wesleyan  University, 
and  while  none  of  them  had  had  practical  experience  as  subjects  of 
respiration  calorimeter  experiments,  all  nervousness  or  apprehension 
had  disappeared  as  the  result  of  the  preliminary  sojourn  of  an  hour 
in  the  chamber.  We  believe  thai  these  men  were  in  as  normal  a 
Btate  of  mind  as  is  the  ordinary  college  student  on  similar  occasions. 
As  a  group  the)   represented  probably  a  fair  average  of  the  studenl 

body.       Ill   -electing  the   men  care   was  taken   to  avoid   those  who  were 

uncertain  as  to  whether  they  could  meet  the  requirements  of  the 
ruination,  and  hence  the  elemenl  of  extre apprehension  com- 
monly experienced  bj  such  students,  an  element  which  might 
well  interfere  seriously  with  a  study  of  the  problems  involved,  was 
eliminated. 


60 

On  the  other  hand,  in  order  to  secure  a  mental  stimulus  and  induce 
a  strong  mental  effort  the  majority  of  the  men  selected  were  those 
who  were  anxious  for  scholarship  prizes  or  some  similar  college  honor. 
In  spite  of  these  attempts  to  secure  the  greatest  mental  exertion 
with  freedom  from  apprehension,  it  will  be  noted  in  reading  the 
record  of  the  mental  impressions  of  the  various  men  that  these  factors 
did  enter  at  times  into  many  of  the  experiments. 

Since  the  metabolism  is  largely  proportional  to  the  body  weight 
of  the  individual,  a  table  of  statistics  of  the  average  weight  at  the 
time  and  size  of  the  subjects  is  given  in  the  following  table,  together 
with  the  age  and  height  of  each  of  the  subjects: 

Statistics  of  age,  height,  and  average  weight  of  subjects. 


No. 

Subject. 

1 

J.  A.  R 

2 

H.  D.  A.... 

3 

H.  G 

4 

F.  N.  C 

5 

J.  v.c 

6 

A.M 

7 

F.  E.  R.... 

8 

J.  W.  H.... 

9 

C.  A.  R.... 

10 

G.  H.  H.... 

11 

H.  L.  W... 

12 

D.  R.  F... 

13 

J.N.  T 

14 

H.  C.  A.... 

15 

F.  C.  B 

16 

G.  E.  H.... 

17 

N.  M.  P.... 

18 

G.  W.  S.... 

19 

A.  G 

20 

H.  L.  K.... 

21 

G.  G.  R.... 

22 

E.M.S.... 

Age. 


Height. 


Weight. 


23  years 

21  years 

22  years 

19  years 

22  years 
21  years 

20  years 
29  years 

18  years 

21  years 

26  years 

23  years 
21  years 
21  years 

23  years 

27  years 
21  years 
20  years 

24  years 
23  years 

19  years 
27  years 


6  months . 
5  months. 
5  months . 
1  month.. 


6  months. 
5  months. 


10  months. 
3  months.. 

11  months. 


10  months . 
4  months . . 
6  months . . 


2  months . 


4  months . . 
10  months. 


5  feet  1)  inches.. 
5  feet  Hi  inchs.. 
5  feet 3  inches... 
5  feet 6  inches.. . 
5  feet 8  inches... 
5  feet9  inches. . . 
5  feet 6  inches... 
5  feet 9  inches.. . 
5  feet  8*.  inches.. 
5  feet 4  inches... 
5  feet4A  inches.. 
.5  feet 8  inches... 
5  feet 8  inches. .. 

5  feet7f  inches.. 

6  feet 

5  feet  10*.  inches. 
5  feet  10*  inches. 
5  feet 8  inches... 
5  feet 7  inches... 
5  feet 5 J  inches.. 
5  feet  10  inches.. 
5  feet  8!;  inches.. 


Kilograms. 
59.3 
65.1 
49.2 
57.8 
63.2 
67.2 
51.5 
60.6 
58.2 
51.6 
52.0 
62.7 
62.7 
58.7 
72.6 
63.2 
70.0 
52.2 
61.3 
57.0 
77.2 
64.1 


STATISTICS  OF  THE  MENTAL  WORK  EXPERIMENTS. 

The  detailed  statistics  of  the  experiments  are  given  in  the  following 
pages.  The  character  of  the  diet  before  the  experiment,  the  per- 
sonal impressions  of  the  subject  during  the  periods,  the  pulse  rate, 
body  temperature,  and  body  weight  at  the  beginning  and  end  of  the 
experimental  period,  are  all  given  as  supplementary  evidence  bearing 
on  the  general  question  of  metabolism. 

METHOD  OF  CALCULATION  OF  BODY  WEIGHT  TO  PERIODS. 

The  procedure  of  calculating  the  body  weight  for  the  beginning 
and  end  of  the  periods  in  these  experiments  needs  some  explanation 
and  was  as  follows: 

There  were  two  weights  taken  of  the  man,  one  at  the  time  he 
entered  the  calorimeter  and  the  other  immediately  after  the  exper- 
iment was  finished.  From  the  difference  in  time  of  these  two 
weights  and  the  change  in  weight  the  amount  of  loss  from  the  time 


61 

of  the  first  weighing  until  the  beginning  of  the  period  was  calculated. 
Also  the  amount  lost  from  the  end  of  the  last  period  to  the  last  weight 
was  calculated.  This  method  of  calculation  assumes  that  the  rate 
of  loss  at  the  beginning  of  the  period  is  practically  the  same  as  at  the 
end.  This  is  probably  not  true,  but  the  actual  difference  between 
the  loss  of  weight  calculated  by  the  above  method  and  the  actual  loss 
is  so  small  as  to  be  negligible.  In  case  urine  was  passed  or  water 
drunk,  the  weight  of  urine  was  added  to  the  end  weight  and  the 
amount  of  water  consumed  subtracted  from  the  end  weight,  so  as  to 
obtain  what  would  correspond  to  the  respiratory  loss.  The  loss  of 
body  weight  as  calculated  by  this  method  is  less  than  would  be 
obtained  if  it  were  calculated  by  the  respiratory  loss.  The  probable 
reason  for  this  is  because  the  materials  inside  the  calorimeter,  such 
as  the  table  and  chair,  lose  weight,  presumably  water,  and  this  loss 
would  be  calculated  in  the  absorption  of  water.  An  example  of  the 
above  method  of  calculation  is  given  below.  The  subject  J.  A.  R. 
in  mental  work  experiment  Xo.  1  weighed  at  S.04  a.  m.  59.367 
kilograms.  At  12.10  p.  m.  he  weighed  59.192  kilograms.  There 
was  thus  a  loss  in  weight  of  0.175  kilogram  in  246  minutes.  The 
first  period  began  at  8.59  a.  m.  Therefore  the  difference  in  time 
between  the  time  of  the  first  weighing  and  the  beginning  of  the  first 
period  was  55  minutes,  and  the  amount  of  loss  would  be  ^55  X  0.175 
kilogram.  This  gives  0.039  kilogram  as  a  loss  from  8.04  to  8.59  a.  in. 
Subtracting  this  from  the  weight  at  8.04  a.  m.  we  have  59.328  kilo- 
grams. Therefore  the  body  weight  at  8.59  a.  m.,  at  the  beginning 
of  the  first  period,  is  59.32S  kilograms.  Similarly,  the  last  weight 
was  taken  at  12.10  p.  m.,and  the  end  of  the  last  period  was  at  11.59 
a.  m.  Therefore  there  was  a  difference  of  11  minutes,  and  ^W  X  0.175 
kilogram  gives  0.008  kilogram  as  the  loss  in  weight  between  11.59 
a.  m.  and  12.10  p.  m.  The  subject  weighed  at  12.10  p.  m.  59.192 
kilograms.  Therefore  at  11.59  a.  in.  he  would  weigh  the  above  weight 
+  0.008,  giving  59.2. kilograms. 

Copies  of  the  examination  papers  are  not  included  in  this  report, 
though  theyhave  been  kept  on  file.  As  has  been  stated  previously, 
it  is  believed  that  they  involved  concentrated  mental  effort  on  the 
part  of  the  subjects. 

MENTAL  WORK  EXPERIMENT  No.   1. 

The  experiment  was  made  with  J.  A.  R.  on  the  forenoon  of  February 
v  L905.  Breakfasl  preceding  the  experiment  consisted  of  an  average- 
!  dish  of  oatmeal  with  sugar  and  milk,  a  large  slice  of  bread,  and 
2  heaping  tablespoonfuls  of  beef  and  potato  kadi. 

The  record  of  impressions  kept  by  the  subject  staled  that  he  suffered 
no  inconvenience  during  the  period  in  the  calorimeter  and  was  not 
disturbed  by  the  noise  of  the  blower  which  forces  the  ventilating  air 


62 


current  through  the  respiration  chamber.  He  had  just  time  during 
the  experimental  period  to  complete  his  examination  paper  and 
reread  it.  No  water  was  drunk  and  no  urine  was  passed  during  the 
experiment. 

The  pulse  rate  was  taken  a  number  of  times  and  was  as  follows: 
8.52  a.  m.  97,  9.57  a.  m.  83,  10.02  a.  m.  87,  10.05  a.  m.  85,  11.36  a.  m. 
73,  11.39  a.  m.  75,  and  11.41  a.  m.  74. 

The  body  temperature  at  8.59  a.  m.,  shortly  after  the  beginning  of 
the  experimental  period,  was  98.5°  F.  and  at  11.59  a.  m.,  shortly 
before  the  close  of  the  experimental  period,  it  was  97.5°  F. 

The  body  weight  at  the  beginning  of  the  experiment,  8.04  a.  m., 
was  59.367  kilograms,  and  at  the  close  of  the  period,  12.10  p.m.,  it 
was  59.192  kilograms. 

The  subject  took  an  examination  in  physics  (thermodynamics), 
writing  1,260  words.  When  the  examination  papers  were  corrected 
it  was  found  that  he  had  secured  first  grade.* 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  1. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 
elimi- 
nated. 

Loss  in 

body 

weight. 

8.59  to  10.29  a.  m 

Grams. 
48.38 
52.18 

Grams. 
51.17 
49.96 

Grams. 
40.01 
37.03 

Calories. 
144. 30 
144.44 

Kilogram. 

10.29  to  11.59  a.  m 

100. 56 

101. 13 

77.04 

288. 74 

0.128 

MENTAL  WORK  EXPERIMENT  No.  2. 

The  experiment  was  made  with  H.  D.  A.  on  the  afternoon  of 
February  8,  1905.  Dinner  eaten  before  the  experimental  period  con- 
sisted of  6  tablespoonfuls  of  vegetable  soup,  a  slice  of  roast  beef  with 
mashed  potatoes,  and  tomatoes,  one-sixth  of  an  apple  pie,  and  a 
medium-sized  cup  of  coffee  with  3  teaspoonfnls  of  sugar,  and  about 
2  teaspoonfuls  of  sugar  were  also  eaten  on  the  pie. 

The  record  kept  by  the  subject  shows  that  he  found  the  air  rather 
poor  at  first,  but  after  a  little  it  was  satisfactory,  the  light  was  fair, 
the  temperature  of  the  respiration  chamber  comfortable,  and  the 
noise  of  the  blower,  though  noticeable,  was  not  disturbing.  The 
actual  work  involved  in  taking  the  examination  required  137  minutes, 
though  he  was  engaged  in  writing  for  the  whole  experimental  period 
of  three  hours. 

The  pulse  rate  taken  at  different  times  was  as  follows:  1  p.  m.  83, 
1.30  p.  m.  77,  1.58  p.  m.  82,  2.30  p.  m.  79,  3  p.  m.  72,  3.30  p.  m.  73, 
4  p.  m.  69,  and  4.30  p.  m.  69. 

aBy  first  grade  is  meant  the  mark  obtained  on  the  examination.  Grades  in  exam- 
inations range  from  1  to  5,  1  being  the  highest  obtainable  and  5  indicating  that  the 
subject  has  not  passed  the  examination.     A  mark  of  4  corresponds  to  60  per  cent. 


63 


At  the  beginning  of  the  experiment,  2.0o  p.  in.,  the  body  temper- 
ature was  US. 7°  F.  and  at  the  end  of  the  period,  5.03  p.  in.,  it  was 
98.3°  F. 

The  body  weight  at  12.-49  p.  m.  was  65.266  kilograms  and  at  the 
close  of  the  experiment,  5.13  p.  m..  65.01  kilograms. 

The  subject  took  the  same  examination  (thermodynamics)  as  the 
subject  of  experiment  Xo.  1,  writing  1,550  words,  in  answering  the 
examination  questions,  and  secured  first  grade. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  .'. 


Time. 


Water 
vapo- 
rized. 


Carbon 

dioxid       Oxygen 

elimi-      absorbed. 

nated. 


Heat 
elimi- 
nated. 


Loss  in 
body 

weight. 


2.03  to  3.33  p.  m 69. 65 

3.33  to  5.03  p.  in 63. 85 

Total  for  3  hours 133. 50 


Grams. 

n.20 

52.80 


Grams.      Calorics. 

178.34 

48.00         164.88 


Kilogram. 


94.00 


343.  22 


MENTAL  WORK  EXPERIMENT  No.  3. 

The  experiment  was  made  with  H.  G.  on  the  forenoon  of  February 
9,  1905.  Breakfast  before  the  experimental  period  consisted  of  a 
shredded-wheat  biscuit,  a  cup  of  coffee,  a  biscuit,  2  tablespoonfuls  of 
sugar,  and  <>ne-half  glass  of  milk. 

A-  shown  by  the  record  which  the  subject  kept,  he  became  accus- 
tomed to  his  surroundings  soon  after  entering  the  respiration  chamber 
and  was  comfortable,  although  he  was  a  little  drowsy  at  first,  owing 
to  the  rather  high  temperature  of  the  respiration  chamber  at  the 
beginning  of  the  experimental  period.  lie  did  not  consider  the  exam- 
ination difficult  and  was  in  no  way  disturbed  by  taking  it  in  the 
respiral  ion  chamber. 

The  pulse  late  as  recorded  at  different  times  during  the  experimental 
period  was  as  follows:  8.10  a.  m.  84,  8.45  a.  m.  89,  9.25  a.m.  84, 
10.05  a.  in.  70.  10.2.-.  a.  m.  74,  10.55  a.  m.  72,  11.30  a.  m.  70, 
11.45  a.  in.  OS,  and  12  noon  07. 

The  body  temperature,  which  was  taken  at  the  beginning  and  end 
of  the  experimental  period,  was  99°  F.  at  9.04  a.  m.  and  98.2°  F. 
at   12.0  1  [..  m. 

The  body  weight  at  8  a.  in.  was  49.279  kilograms  and  at  12.12  p.  m. 
it  was  10. 103  kilograms. 

The  subjeel  took  an  examination  in  evolution,  and  in  answer  to  ten 
questions  wrote  2,000  words.  When  the  examination  papers  were 
corrected  he  was  given  third  grade, 


64 


Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  3. 


Water 
vapo- 
rized. 


Carbon 
dioxid 
elimi- 
nated. 


Oxygen 
absorbed, 


Heat 
elimi- 
nated. 


Loss  in 

body 

weight. 


9.04  to  10.34  a.  m 

10.34  a.  m.  to  12.04  p.  m 

Total  for  3  hours.. 


Grams. 
52.64 
53.48 


Grams. 
44.62 
37.32 


Grams. 
45.62 


Calorics. 
140.  91 
126. 17 


Kilogram. 


267.  08 


MENTAL  WOBK  EXPERIMENT  No.  4. 

The  experiment  was  made  with  F.  N.  C.  on  the  afternoon  of  Feb- 
ruary 9,  1905.  Lunch  before  the  experimental  period  consisted  of  a 
little  roast-beef  hash  with  creamed  potatoes,  a  slice  of  bread  and 
butter,  and  a  portion  of  apple  tapioca  pudding. 

The  subject  found  the  air  and  light  in  the  respiration  chamber  sat- 
isfactory and  was  not  disturbed  by  the  sound  of  the  rotary  blower, 
though  he  found  that  the  rattling  of  the  metallic  shields  used  to  regu- 
late the  heat  absorption  system  was  somewhat  disturbing.  In  gen- 
eral, he  found  the  confinement  in  the  respiration  chamber  rather 
monotonous,  though  he  states  that  he  could  as  well  take  the  examina- 
tion there  as  in  the  regular  class  room. 

The  pulse  rate  was  recorded  several  times  as  follows:  2.08  p.  m.  66, 
2.45  p.  m.  72,  3.18  p.  m.  72,  3.45  p.  m.  66,  4.12  p.  m.  60,  4.40  p.  m.  66, 
and  4.55  p.  m.  72. 

The  body  temperature  was  taken  at  the  beginning  and  at  the  close 
of  the  experimental  period,  being  98.1°  F.  at  2.05  p.  m.  and  97.8°  F. 
at  5.05  p.  m. 

The  body  weight  at  1.05  p.  m.  was  57.943  kilograms  and  at  5.13 
it  was  57.75  kilograms. 

The  subject  took  an  examination  in  chemistry,  writing  about  1,200 
words  and  securing  second  grade.  The  details  of  the  experiment 
follow : 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  4. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 
elimi- 
nated. 

Loss  in 

body 

weight. 

2.05  to  3.35  p.  m 

Grams. 
57.93 
53.85 

Grams. 
54.18 
51.91 

Grams. 
39.74 
37.34 

Calorics. 
158.55 
152. 10 

Kilogram. 

3.35  to  5.05  p.  m 

Total  for  3  hours 

111.78 

106.  09 

77.08 

310. 65 

0.140 

65 


MENTAL  WORK  EXPERIMENT  No.  5. 

The  experiment  was  made  with  J.  A'.  C.  on  the  forenoon  of  February 
10,  1905.  Breakfast  before  the  experimental  period  consisted  of  a 
dish  of  oatmeal  with  sugar  and  milk,  a  small  plate  of  hash,  and  a  cup 
of  coffee  with  sugar  and  milk. 

Though  a  little  drowsy  at  first,  the  subject  states  that  he  was  per- 
fectly comfortable  in  the  respiration  chamber  during  the  experimental 
period.     He  drank  42  cubic  centimeters  of  water. 

The  pulse  rate  as  taken  at  intervals  was  as  follows:  8.10  a.  m.  82, 
B.58  a.m.  77.  10.03  a.  m.  71, 10.30  a.  m.  69, 11  a.m.  67,  and  12  noon  73. 

Records  for  body  temperature  were,  at  9.01  a.  m.  98.3°  F.,  and  at 
12.(11  p.m.  98.3°  F. 

The  body  weight  was  63.306  kilograms  at  7.57  a.  m.  and  63.121 
kilograms  at  12.09  p.  m. 

The  subject  took  an  examination  in  English  literature,  writing  2,200 
words,  and  secured  second  grade. 

Carbon  dioxid,  miter  vapor,  mid  heat  eliminated  and  oxygen  absorbed,  experiment  No.  5. 


Time. 

Wii,.r      Carbon 

rized      1     elum" 
mea-        nated. 

Oxygen 
absorbed. 

Heat 
elimi- 
nated. 

Loss  in 

body 
weight. 

1.01  to  10.31  a.  m... 

Grams. 
63.59 
67.70 

Grams. 
49.  S7 

Grams. 
44.22 
44.18 

Calories. 
153.65 
148. 93 

Kilogram. 

.   m.  to  12.01  p.  m  

131.29         101  till 

88.40 

302.58 

0.132 

MENTAL  WORK  EXPERIMENT  No.  6. 

The  experiment  was  made  with  A.  M.  on  the  afternoon  of  Febru- 
ary 10.  19(15.  Dinner,  which  was  eaten  shortly  before  the  experiment 
began,  consisted  of  two  small  pieces  of  roast  heel',  a  little  potato, four 
-lice-  (.f  bread,  a  piece  of  squash  pie,  and  a  cup  of  coffee. 

Though  a  little  warm  ;it  first,  the  subject  was  soon  comfortable 
and  remained  so  throughout  the  experimental  period.  He  states 
th.it  lie  found  the  examination  very  long,  though  not  particularly 
Difficult,  and  that  he  was  so  busily  engaged  that  he  perspired  notice- 
ably. During  the  experimental  period  he  drank  61  cubic  centimeters 
of  water. 

The  pulse  Pate  ;i>  recorded  ;tl    different    limes  was  as  follows:    1.45 
p.  in.  87,  '■',  \>.  in.  79,  1  p.  in.  77.  and  L30  \>.  m.  77. 
The  body  temperature  al  2.01  p.m.  was  99.2°  F.  and  ;it  5.01  p.m. 

F. 
The  body  weighl  was  taken  twice,  being  67.285  kilograms  .it   L2.53 
p.  in.  and  66.942  kilograms  ;ii  5.1  I  p.  m. 
70076     Bull    208     09     -5 


66 

The  subject  took  the  same  examination  in  English  literature  as 
the  subject  in  experiment  No.  5,  wrote  2,400  words,  and  obtained 
second  grade. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,,  experiment  No.  6. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 

jiated. 

Oxygen 
absorbed. 

Heat 
elimi- 
nated. 

Loss  in 

body 

weight. 

Grams. 
74.89 

Grams. 
59.83 
54.11 

Grams. 

Calories. 
189.  78 
170. 33 

Kilogram. 

73.87 

34.36 

148. 76 

113.94 

360. 11 

0.237 

MENTAL  WORK  EXPERIMENT  No.  7. 

The  experiment  was  made  with  F.  E.  R.  on  the  forenoon  of  Feb- 
ruary 11,  1905.  Breakfast  before  the  experimental  period  consisted 
of  a  small  dish  of  oatmeal  and  a  cup  of  coffee  with  milk  and  sugar. 

Though  rather  nervous  at  first,  the  subject  states  that  he  soon 
became  quite  collected  and  felt  that  he  could  take  the  examination 
as  easily  as  in  the  class  room.  He  found  the  temperature  of  the  res- 
piration chamber  a  little  too  high  for  comfort. 

The  pulse  rate,  which  was  taken  at  intervals,  was  as  follows:  7.56 
a.  m.  58,  8.07  a.  m.  94,  8.18  a.  m.  104,  8.44  a.  m.  101,  8.55  a.  m.  101, 
10.35  a.  m.  88,  11.06  a.  m.  89,  11.29  a.  m.  88,  11.47  a.  m.  91,  and 
12.03  p.  m.  90. 

The  body  temperature  at  9.01  a.  m.  was  99.7°  F.  and  at  12.01  p.  in. 
99.4°  F. 

The  body  weight  at  7.52  a.  m.  was  51.618  kilograms  and  at  12.09 
p.  m.  51.409  kilograms. 

The  subject  considered  that  the  examination  paper  in  psychology 
with  which  he  was  engaged  was  rather  difficult  and  required  con- 
siderable thought.     He  secured  first  grade. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  7. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat' 
elimi- 
nated. 

Loss  in 

body 

weight. 

9.01  to  10.31  a.  m 

Grams. 
61.45 
58.13 

Grams. 
45.17 
43.90 

Grams.       Calories. 
33.87         143.45 
36.35         134.81 

Kilogram. 

10.31  a.  m.  to  12.01  p.  m 

119.58 

89.07 

70.22 

278. 26 

0.146 

67 

MENTAL  WORK  EXPERIMENT  No.  8. 

The  experiment  was  made  with  J.  W.  II.  on  the  afternoon  of  Feb- 
ruary 11,  1905.  Dinner  taken  shortly  before  the  experimental 
period  consisted  of  2  slices  of  boiled  ham  with  cabbage  and  potatoes, 
1^  slices  of  bread  and  butter,  a  piece, of  apple  pie,  and  1  large  cup  of 
coffee. 

The  subject  states  that  he  felt  comfortable  all  the  time  he  was  in 
the  respiration  chamber,  though  he  was  rather  tired  from  the  uni- 
versity work  in  which  he  was  engaged  on  preceding  days.  He  drank 
191  cubic  centimeters  of  water  during  the  experiment. 

The  pulse  rate  was  recorded  as  follows:  1.20  p.  n\.  87,  2  p.  m.  96, 
3  p.  m.  87,  4  p.  m.  To,  and  4.50  p.  m.  74. 

The  body  temperature  at  1.  5.*)  p.  m.  was  (is.!)0  F.  and  at  4.").")  p.  m. 
it  was  98°  F. 

The  body  weight  at  12.45  p.  m.  was  60.688  kilograms  and  at  5.02 
p.  in.  60.406  kilograms. 

In  answering  the  examination  questions  in  physics  with  which  he 
was  engaged  the  subject  wrote  1,150  words  and  secured  third  grade. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  8. 


Time. 

Watej 
rized. 

dioxid 
elimi- 
nated. 

Oxygen 

alisiirl.nl. 

Beat 
elimi- 
nated. 

Loss  in 

bodj 

weight. 

Grams. 
64.50 

73.09 

Grams. 
61.28 
55.  59 

annus. 
56.  L7 
40.53 

180.28 
168.  L6 

Kilogram. 

Total  for  3  hours 

137.50          110.87 

96.  70 

348.  44 

0.197 

MENTAL  WORK  EXPERIMENT  No.  9. 

The  experiment  was  made  with  ( '.  A.  K.  on  the  forenoon  of  Febru- 
ary 13,  1905.  Breakfast  shortly  before  the  experimental  period  con- 
sisted of  a  large  glass  of  milk  and  a  dish  of  cereal  breakfast  food. 

The  subject  states  that  though  he  had  had  little  sleep  on  the  night 
preceding  the  experiment,  and  so  was  rather  tired,  he  did  not  find  the 
confinement  in  the  respiration  chamber  at  all  disagreeable  and  con- 
sidered the  conditions  entirely  sat  isfactory  for  taking  an  examinat  i<m. 

The  pulse  rate  as  recorded  was  as  follows:  8.30  a.  m.  90,  9  a.  m.  82, 
9.25  a.  m.  S2,  9.45  a.  m.  78,  10.10  a.  m.  76,  10.45  a.  m.  76,  LI. 15  a.  m. 
72,  1  1.4.5  a.  in.  70.  and  12  noon  70. 

The  body  t  emperat  ure  at  9  a.  HI.  Was  99.2     F.  and  at    12  noon  98      F. 

The  body  weight   was   58.318  kilograms  at  7.56  a.  m.  and   58.13 
kilograms  at    I  2.09  p.  m. 
The  subject  took  an  examinal  ion  in  French,  securing  second  grade. 

lie  v.  rote  )  ,S00  words. 


68 


Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  9. 


Time. 


9  to  10.30  a.  m 

10.30  a.m.  to  12  noon. 

Total  for  3  hours 


Water 
vapo- 
rized. 


Grams. 
54.92 
57.86 


Carbon 
dioxid 
elimi- 
nated. 


Grams. 
48.90 
43. 24 


92.14 


Oxygen 
absorbed. 


Grams. 
37.11 


Heat 
elimi- 
nated. 


Calories, 
160. 85 
149. 13 


309. 98 


Loss  in 
body- 
weight. 


Kilogram. 


MENTAL  WORK  EXPERIMENT  No.   10. 

The  experiment  was  made  with  G.  H.  H.  on  the  forenoon  of  Febru- 
ary 14,  1905.  Breakfast  preceding  the  experiment  consisted  of  a  dish 
of  dry  cereal  breakfast  food,  with  sugar  and  milk,  2  slices  of  corn 
bread,  and  a  glass  of  milk. 

Though  somewhat  nervous,  owing  to  confinement  in  the  respiration 
chamber,  the  subject  felt  that  he  did  as  well  with  the  examination  as 
he  could  have  done  under  usual  circumstances  in  the  class  room.  He 
considered  the  examination  rather  difficult. 

The  pulse  rate  wras  recorded  as  follows:  9.10  a.  m.  114,  10  a.  m.  124, 
10.35  a.  m.  118,  11.15  a.  m.  106,  12  noon  120,  and  12.25  p.  m.  119. 

The  body  temperature  was  not  taken. 

The  body  weight  at  the  beginning  of  the  experiment,  8.23  a.  m., 
was  51.656  kilograms  and  at  the  close,  12.37  p.  m.,  51.484  kilograms. 

The  subject  of  trie  examination  paper  wnth  which  he  was  engaged 
was  economics,  and  second  grade  was  obtained. 


Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No. 


10. 


Water 
vapo- 
rized. 


Carbon 
dioxid 
elimi- 
nated. 


Oxygen 
absorbed. 


Heat 
elimi- 
nated. 


Loss  in 

body 

weight. 


9.23  to  10.32  a.  m 

10.32  a.  m.  to  12.32  p.  m 

Total  for  3  hours  9  minutes 


Grams. 
38.05 
66. 15 


Grams. 
36.19 
62.29 


Grams. 
32.72 
45.23 


Calories. 
107. 35 
177. 09 


Kilogram. 


104. 20 


284.  44 


0.141 


MENTAL  WORK  EXPERIMENT  No.   11. 

The  experiment  was  made  with  H.  L.  W.  on  the  afternoon  of  Feb- 
ruary 14,  1905.  Dinner  preceding  the  experimental  period  consisted 
of  a  small  portion  of  roast  beef,  a  small  potato  with  butter,  a  portion  of 
tomatoes,  and  an  apple  dumpling. 

The  subject  found  the  sound  of  the  blower  and  other  machinery  in 
the  respiration  chamber  rather  soothing  than  otherwise.  He  finished 
the  examination  paper  and  read  it  over  carefully  about  an  hour  before 
the  close  of  the  experimental  period  and  rested  until  the  experiment 
closed. 


69 

The  pulse  rate  was  recorded  a  number  of  times  as  follows:  1 .30  p.  m. 
76,  2.14  p.  m.  86,  2.45  p.  m.  SS.  3.25  p.  m.  88,  4  p.  m.  72.  4.34  p.  m. 
72,  and  4.55  p.  m.  69. 

The  body  temperature  at  2.02  p.  m.  was  99.5°  F.  and  at  5.02  p.  ni. 
98.6°  F. 

The  body  weight  at  12.54  p.  m.  was  52.040  kilograms  and  at  5.11 
p.  m.  51.855  kilograms. 

The  subject  was  engaged  with  an  examination  paper  on  economics 
and  secured  third  grade. 

Carbon  dioxid,  water  vapor,  mid  heat  eliminated  and  oxygen  absorbed,  experiment  No.  11. 


Tim.'. 

Water 

vapo- 
rized. 

Curium 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heal 

elimi- 
nated. 

Loss  in 
body 

weight. 

2.02  to  3.32  p.  in 

Orams. 
02.24 
61.66 

Grams. 
40.44 
39. 22 

Grams. 
38.58 
32.05 

( alorii  s. 
148.52 

144. 99 

Kilogram. 

3.32  to  5.02  p.  m 

Total  for  3  hours 

123.  90 

85.60 

70.63 

293. 51 

0  133 

MENTAL  WORK  EXPERIMENT  No.    12. 

The  experiment  was  made  with  D.  R.  F.  on  the  forenoon  of  Feb- 
ruary 15,  1905.  Breakfast  before  the  experimental  period  consisted 
of  1  shredded-wheat  biscuit,  a  portion  of  cooked  cereal  with  milk  and 
sugar.  1  hot  roll,  and  some  dates. 

In  general  the  subject  found  his  sojourn  in  the  respiration  cham- 
ber comfortable  though  novel. 

The  pulse  rate  was  recorded  at  intervals  as  follows:  8.20  a.  m.  70, 
9.05  a.  m.  83,  10  a.  m.  07,  10.35  a.  in.  64,  11.12  a.  in.  02,  and  12.10 
p.  in.  62. 

The  body  temperature  at  9.04  a.  m.  was  98°  F.  and  at  12.04  p.  m. 
97.8°  F. 

The  body  weight  at  8.08  a.  m.  was  02.20S  kilograms  and  at  12.13 
j).  m.  02.1  13  kilograms. 

In  answering  the  questions  in  the  examination  in  English  literature 
with  which  the  subject  was  engaged  be  wrote  2,400  words,  and 
Becured  firsl  grade. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  I '. 


Tim.-. 

Water 
rlzed. 

Carbon 

dioxid 

elimi- 
nated, 

Heal 
nated. 

i  .. 
bodj 
weight. 

63  .'.7 

1 

Kilogs 

.VI.  .'7 

.:l  16 

103.84 

0  in 

70 


MENTAL  WORK  EXPERIMENT  No.   13. 

The  experiment  was  made  with  J.  N.  T.  on  the  afternoon  of  Feb- 
ruary 15,  1905.  Dinner,  which  was  eaten  shortly  before  the  experi- 
mental period,  consisted  of  a  large  slice  of  roast  beef,  with  mashed 
potatoes,  and  stewed  tomatoes,  a  small  piece  of  apple  pie,  and  a  large 
cup  of  coffee. 

The  records  kept  by  the  subject  state  that  when  he  first  entered 
the  respiration  chamber  he  found  the  temperature  rather  high.  He 
soon  became  comfortable.,  however,  and  was  in  no  way  inconven- 
ienced, but  rather  considered  the  conditions  satisfactory  for  taking 
an  examination.  Toward  the  close  of  the  experimental  period  the 
temperature  was  rather  cool. 

The  pulse  rate  as  recorded  at  intervals  was  as  follows:  1.20  p.  m. 
97,  2.35  p.  m.  83,  3.11  p.  m.  82,  and  4.53  p.  m.  70. 

The  body  temperature  at  2.01  p.  m.  was  99.4°  F.  and  at  5.01  p.  m. 
98.8°  F. 

The  body  weight  at  1  p.  m.  was  62.77  kilograms  and  at  5.11  p.  m. 
62.49  kilograms. 

The  subject  was  engaged  with  an  examination  in  physics,  writing 
1,050  words,  and  secured  second  grade. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  13. 


Time. 

"Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 
elimi- 
nated. 

Loss  in 

body 

weight. 

2.01  to  3.31  p.  171 

Grams. 
67.90 

Grams. 
67.98 
56.23 

Grams. 
50.66 
44.14 

Calories. 
201.86 
179.  99 

Kilogram. 

3.31  to  5.01  p.  in 

136. 71 

124. 21 

94.80 

MENTAL  WORK  EXPERIMENT  No.   14. 

The  experiment  was  made  with  H.  C.  A.  on  the  forenoon  of  Feb- 
ruary 16,  1905.  Breakfast  shortly  before  the  experimental  period 
consisted  of  a  cup  of  coffee  with  a  small  quantity  of  sugar  and  milk 
and  6  buckwheat  cakes  with  butter  and  sirup. 

The  records  kept  by  the  subject  show  that  he  was  entirely  com- 
fortable in  the  respiration  chamber  and  was  busy  during  the  whole 
period  with  his  examination. 

The  pulse  rate  recorded  at  intervals  was  as  follows:  9  a.  m.  85, 
11.25  a.  m.  63,  11.55  a.  m.  59,  and  12.24  p.  m.  60. 

The  body  temperature  at  9.24  a.  m.  was  98.9°  F.  and  at  12.24  p.  m. 
97.9°  F. 

The  body  weight  at  8.01  a.  m.  was  58.882  kilograms  and  at  12.32 
p.  m.  58.663  kilograms. 


71 

The  subject  was  engaged  with  an  examination  in  advanced  analyt- 
ical geometry,  and  secured  second  grade. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  14. 


Water       Carbon 
r-m  '■        nated. 

Oxygen 
absorbed. 

Heal          Loss  in 
elimi-           body 
nated.        weight. 

Grams.       Grams. 
9.°4  to  10.54  a.  m 40. 84           52.  16 

Grams. 
36.06 

38.51 

Calories. 
151. 07 
L43.69 

Kilogram. 

Hi. .VI  a.  m.  to  12.2-4  p.  in 48.27          50.  in 

Total  for  3  hours 95. 11 

102.56 

74.57 

294. 7G 

0.146 

MENTAL  WORK  EXPERIMENT   No.   15. 

The  experiment  was  made  with  F.  C.  B.  on  the  afternoon  of  Feb- 
ruary 16,  1905.  Dinner  shortly  before  the  experimental  period  con- 
sisted of  2  small  slices  of  roast  beef,  1  potato,  a  slice  of  bread  and 
butter,  a  cup  of  coffee  with  milk,  and  a  small  piece  of  mince  pie. 

The  records  kept  by  the  subject  show  that  he  found  the  respira- 
tion chamber  rather  cramped  quarters,  though  in  general  as  satis- 
factory for  examination  purposes  as  the  ordinary  class  room.  In  his 
opinion  the  examination  called  for  a  moderate  amount  of  mental 
work.  It  was  noticed  by  the  observer  who  recorded  the  experimental 
data  that  the  subject  was  rather  nervous  and  moved  his  arms  and 
hands  about  more  than  the  other  subjects. 

The  pulse  rate  as  recorded  at  intervals  was  as  follows:  1..").")  p.  ni.  94, 
2.45  p.  in.  88,  3.30  p.  m.  84,  4.30  p.  m.  83,  5.20  p.  m.  79.  5.40  p.  m.  83, 
and  5.50  ]).  m.  76. 

The  body  temperature  at  2.05  p.  m.  was  00.2°  F.  and  at  n.^'A  p.  in. 
98.9     V. 

The  body  weight  at  12.59  p.  m.  was  72.745  kilograms  and  at  6.07 
p.  in.  72.40  kilograms. 

The  subject  was  engaged  with  an  examination  paper  in  philosophy, 
and  secured  first  grade. 

Carbon  dioxid,  mil,,-  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  t5. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

l|,;,l 

elimi- 
nated. 

Loss  in 

body 
weignt. 

• 

102  B2 

",  i  :.  i 

is  no 

Cillariis. 
177.  S3 
264  69 

Kilogram. 

BO  in 

143  '■! 

0.211 

72 


MENTAL  WORK  EXPERIMENT   No.   16. 

The  experiment  was  made  with  G.  E.  H.  on  the  forenoon  of  Feb- 
ruary 17,  1905.  Breakfast  before  the  experimental  period  consisted 
of  a  dish  of  rolled  oats  with  milk  and  part  of  a  muffin. 

The  record  kept  by  the  subject  shows  that  he  had  a  slight  headache, 
but  this  he  feels  sure  was  in  no  way  caused  by  his  sojourn  in  the  respi- 
ration chamber,  as  otherwise  he  felt  entirely  comfortable. 

The  pulse  rate  as  recorded  was  as  follows:  9.05  a.  m.  65,  10  a.  m.  73, 
11  a.  m.  70,  and  11.55  a.  m.  71. 

The  body  temperature  at  9.05  a.  m.  was  98.4°  F.  and  at  12.05  p.  m. 
98.3°  F. 

The  body  weight  at  7.58  a.  m.  was  63.332  kilograms  and  at  12.14 
p.  m.  63.17  kilograms. 

In  this  experiment  economics  was  the  subject  of  the  examination 
paper,  and  second  grade  was  secured. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  16. 


1    Water 

Time.                                        >     vapo- 

|    rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 
elimi- 
nated. 

Loss  in 

body 

weight. 

9.05  to  10.35  a.  m 

Grams. 
52.43 
45. 18 

Grams. 
44.15 
38.  52 

Grams. 

Calories. 
143.  90 
121. 98 

Kilogram. 

10.35  a.  m.  to  12.05  p.  m 

30.24 

97.61 

82.67 

265. 88 

0.114 

MENTAL  WORK  EXPERIMENT   No.   17. 

The  experiment  was  made  with  N.  M.  P.  on  the  afternoon  of  Feb- 
ruary 17,  1905.  Dinner,  which  was  eaten  shortly  before  the  experi- 
ment began,  consisted  of  soup,  roast  pork  with  potatoes,  fish  cro- 
quettes, a  little  succotash,  tomatoes,  bread  and  butter,  and  apple  pie. 

The  subject  stated  that  he  was  rather  nervous  at  first,  though  the 
feeling  soon  passed  away.  He  did  not  have  time  to  complete  his 
examination  paper,  though  he  did  not  consider  it  as  difficult  as  he 
had  expected. 

The  pulse  rate  as  recorded  at  intervals  was  as  follows:  1.25  p.  m.  80, 
1.55  p.  m.  72,  2.35  p.  m.  68,  3.25  p.  m.  63,  4.07  p.  m.  58,  and  5.05 
p.  m.  54. 

The  body  temperature  at  2.02  p.  m.  was  98.9°  F.  and  at  5.02  p.  m. 
98.5°  F. 

The  body  weight  at  12.50  p.  m.  was  70.133  kilograms  and  at  5.12 
p.  m.  69.875  kilograms. 

The  subject  was  engaged  with  an  examination  in  mathematics, 
and  secured  first  grade. 


73 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  17. 


Time. 


Carbon 

ffiffi 
nated. 


Water 


rized. 


absorbed. 


Ileal  Loss  in 

eliml-  body 

nated.         weight. 


Kilogram. 


Grams.  Grams.  Grams.  Calories. 

72.02  to  3.32  p.  m 66.03  .59.23  49.85  L87.50 

3.32  to 5.02  p.  m 70.42  55.65  42.73  L78.56 

Total  for  3  hours 136.45  114.88  92.58  -                       0.177 


MENTAL  WORK  EXPERIMENT   No.   18. 

The  experiment  was  made  with  G.  W.  S.  on  the  forenoon  of  Febru- 
ary IS,  1905.  Breakfast,  eaten  shortly  before  the  experimental  period 
began, consisted  of  2  dishes  of  oatmeal,  1  muffin,  and  a  cup  of  coffee. 

As  shown  by  the  record  kept  by  the  subject,  he  was  a  little  disturbed 
at  first  by  his  unfamiliar  surroundings, but  soon  became  accustomed 
to  the  respiration  chamber. 

The  pulse  rate  as  recorded  at  intervals  was  as  follows:  8.40  a.  m. 
70,  9.50  a.  m.  So.  10.20  a.  m.  88,  10.50  a.  m.  81,  11.30  a.  m.  76,  and 
1 1.55  a.  m.  SI. 

The  body  temperature  at  s..")«)  a.  m.  was  9S.6°  F.  and  at  11.59 
a.  m.  98.8°  F. 

The  body  weight,  which  was  recorded  as  usual  at  the  beginning  and 
the  end  of  the  experiment,  was  52.227  kilograms  at  8.05  a.  m.  ami 
52.073  kilograms  at  12.08  p.  m. 

German  was  the  subject  of  the  examination, and  second  grade  was 
secured. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  is. 


Time. 

Water 

vapo- 
rized. 

Carbon 

'li"\i'l 

elimi- 
nated. 

11        ,'lmn 
absorbed.     J™ 

body 

HI... 

r,1.7.-, 
17.  58 

49.  76 

I.;  'in 

crams.      Calories, 
I.;  32         138  '"i 
.'•1  S7           131.  1" 

■  l.  m 

92.76 

270.39 

0.114 

MENTAL  WORK  EXPERIMENT    No.    19. 

The  experiment  was  made  with  A.  ( i.  on  t  he  afternoon  of  February 
In,  1905.  Dinner, eaten  shortly  before  the  experimental  period, con- 
listed  of  2  small  pieces  of  ham,  2  potatoes,  ;i  slice  <<\'  bread  ami  butter, 
and  ;i  portion  of  rice  pudding. 

The  record  kept  by  the  subject  showed  that  he  found  his  surround- 
Bgfi  perfectly  comfortable  and  \\  ;i-  in  no  way  disturbed  by  his  sojourn 
in  t  he  respiration  chamber. 


74 

The  pulse  rate  recorded  at  intervals  was  as  follows:  3.45  p.  m.  78, 
4  p.  m.  84,  4.30  p.  m.  83,  4.50  p.  m.  81,  and  5  p.  m.  79. 

The  body  temperature  at  2.07  p.  m.  was  98.6°  F.  and  at  5.07  p.  m. 
98.2°  F. 

The  body  weight  at  1.05  p.  m.  was  61.428  kilograms  and  at  5.17 
p.  m.  61.254  kilograms. 

In  answering  the  examination  questions  in  physics  with  which  he 
was  engaged  the  subject  wrote  1,125  words,  and  obtained  second 
grade. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  19. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 
elimi- 
nated. 

Loss  in 

body 

weight. 

2.07  to  3.37  p.  m-.-i. 

Grams. 
54.03 
58.23 

Grams. 
50.04 
50.04 

Grams. 
44.68 
37. 72 

Calories. 
145.  74 

Kilogram. 

3.37  to  5.07  p.  m 

149. 26 

112. 26 

100. 08 

82.40 

295. 00 

0.124 

MENTAL  WORK  EXPERIMENT  No.  20. 

The  experiment  was  made  with  H.L.  K.  on  the  forenoon  of  Febru- 
ary 20,  1905.  Breakfast,  taken  shortly  before  the  experiment  began, 
consisted  of  1  banana,  4  tablespoonfuls  of  a  dry  ready-to-eat  cereal, 
15  teaspoonfuls  of  cream,  a  cup  of  coffee  with  10  teaspoonfuls  of  cream, 
1  hard-boiled  egg,  a  biscuit,  and  a  doughnut. 

The  subject  stated  that  he  was  somewhat  nervous  in  the  respiration 
chamber,  but  no  more  so  than  in  any  place  with  which  he  was  not 
familiar.  The  light  was  more  satisfactory  than  he  had  expected. 
Urine  was  excreted,  but  the  amount  is  not  recorded. 

The  pulse  rate  was  as  follows:  8.28  a.  m.  103,  8.35  a.  m.  95, 
8.40  a.  m.  103,  8.45  a.  m.  93,  8.57  a.  m.  98,  9.20  a.  m.  103,  9.35 
a.  m.  98,  9.50  a.  m.  97,  10.08  a.  m.  98,  10.45  a.  m.  88,  10.55  a.  m. 
90,  11.40  a.  m.  91,  and  11.55  a.  m.  105. 

The  body  temperature  at  8.59  a.  m.  was  98.9°  F.  and  at  11.59  a.  m. 
98.9°  F. 

The  body  weight  at  8.03  a.  m.  was  57.132  kilograms  and  at  12.09 
p.  m.  56.943  kilograms. 

In  answering  the  questions  in  the  theoretical  chemistry  examina- 
tion with  winch  he  was  engaged  the  subject  wrote  1,690  words,  and 
secured  first  grade. 


75 


Carbon  dioxid,  water  vapor,  andheat  eliminated  and  oxygen  absorbed,  experiment   ' 


Time. 

\\  ater 
rized. 

dioxid 
elimi- 
nated. 

absorbed. 

Heal 
elimi- 
nated. 

Loss  in 
weight. 

10.29  a.  m 

54.94 
50.24 

Grams. 
48.05 
43.  70 

Grams. 
33.37 
30.88 

Calories. 
148.30 
137.62 

Kilogram. 

.»  11.59  a.  in 

Total  for:!  hoars , 

105. 18           01-81            "II  °''         5»s  ''•'                 ii  i»o 

' 

MENTAL  WORK  EXPERIMENT  No.   21. 

The  experiment  was  made  with  (i.  (1.  R.  on  the  forenoon  of  Febru- 
ary 21,  1905.  Breakfast,  which  had  been  eaten  shortly  before  the 
experimental  period,  consisted  of  shredded-wheat  biscuit  and  milk, 
an  omelet,  and  a  cup  of  coffee. 

The  subject  states  that  he  paid  little  attention  to  his  surroundings, 
that  the  light  was  good,  and  that  the  temperature  was  satisfactory, 
though  at  first  a  little  high. 

The  pulse  rate  as  recorded  at  intervals  was  as  follows:  8.56  a.  m. 
99,  9.43  a.  m.  85,  10.2s  a.  m.  83,  and  11.20  a.  m.  SO. 

The  body  temperature  at  9  a.  m.  was  99.3°  F.  and  at  12  noon 
98.9°  F. 

The  body  weight  at  8.07  a.  m.  was  7S.494  kilograms  and  at  12.12 
p.  m.  7s. 25:!  kilograms. 

Mathematics  was  the  subject  of  the  examination  in  this  experiment, 
and  first  grade  was  secured. 

Carbon  dioxid,  water  vapor,  andheat  eliminated  and  oxygen  absorbed,  <  tperimeni  No.   '/. 


Tim.'. 

W'alor 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 
elimi- 
nated. 

Loss  in 

body 

weight. 

.  i  a.  in                  

65.  67 

62.  Hi 

(1  III  HIS. 

53.10 

Gin  ins. 

■:,7.  13 
15.  92 

181.35 
165.91 

Kilogram. 

127.83 

108.78 

83.05 

0. 177 

MENTAL  WORK  EXPERIMENT  No.  22. 

The  experiment  was  made  with  E.  M.  S.  on  the  afternoon  of  Feb- 
ruary 21,  1905.  Lunch,  shortly  before  the  experiment  began,  con- 
d  of  crackers  and  milk. 

The  subjed  stated  thai  he  was  not  at  all  nervous  while  in  the 
Inspiration  chamber.  At  the  beginning  of  the  period  the  tempera- 
lure  was  r;ii her  high  and  ;it   the  close  rather  low.     lie  passed   170 

ns  of  urine 
The  pulse  rate  record  \\;i-  as  follows:   l.Ki  p.  m.  93,  1.57  p.  m.  92, 
■l.-\  I  p.  in.  'is.  3.02  p.  in.  95,  3.43  p.  m.  89,  and  1.50  p.  m.  7  1. 


76 

The  body  temperature  at  2  p.  m.  was  99.3°  F.  and  at  5  p.  m. 
98.5°  F. 

The  body  weight  at  12.51  p.  m.  Was  64.211  kilograms  and  at  5.09 
p.  m.  63.995  kilograms. 

The  subject  wrote  328  words  in  answering  an  examination  in 
calculus,  and  obtained  fourth  grade. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  2:1. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

ITeat 
elimi- 
nated. 

Loss  in 

body 

weight. 

Grams. 
56.25 
58.62 

Grams. 
53.22 
49.95 

Grams. 
41.13 
34.22 

Calories. 
165. 05 
160. 24 

Kilogram. 

114.87 

103. 17 

75.35 

325.  29 

0.150 

SUMMARY  OF  RESULTS  OF  MENTAL  WORK  EXPERIMENTS. 

In  the  following  table  the  results  obtained  during  the  mental  work 
tests,  so  far  as  the  respiratory  gases  and  heat  production  are  con- 
cerned, are  recorded.  It  will  be  observed  that  in  a  number  of 
instances  the  determinations  of  oxygen  are  lacking.  In  those  experi- 
ments in  which  it  was  obtained  it  was  found  that  the  respiratory 
quotient  was  on  the  average  0.913,  the  carbon  dioxid  thermal  quo- 
tient 33.88,  and  the  oxygen  thermal  quotient  27.5.  A  special  dis- 
cussion of  these  results  as  indexes  of  the  general  trend  of  normal 
metabolism  is  out  of  place  here.  The  results  are  brought  together 
in  the  table  simply  for  the  purpose  of  convenience. 

From  the  tabular  statements  given  in  connection  with  each  experi- 
ment the  figures  from  the  following  table  can  be  readily  deduced, 
with  the  exception  of  the  heat  production,  which  is  calculated  from 
the  actual  amount  of  heat  measured  by  the  calorimeter  as  recorded 
in  the  tables  with  each  experiment,  a  value  which  does  not  cor- 
rectly represent  the  total  heat  production  during  the  corresponding 
period.  For  example,  if  the  temperature  of  the  body  is  lowered  1°  C, 
the  body  may  be  said  to  have  cooled  this  amount,  and  therefore  to 
have  lost  by  simple  radiation  sufficient  heat  to  warm  the  body  1°  C. 
The  specific  heat  of  the  body  is  commonly  taken  as  0.83,  and  hence  a 
man  weighing  60  kilograms  would  lose  nearly  50  calories  of  heat  if 
the  body  temperature  became  lowered  1°.  Furthermore,  if  the  body 
loses  weight  there  is  heat  lost  corresponding  to  the  cooling  of  the 
weight  of  body  material  from  the  temperature  of  the  body  to  that  of 
the  calorimeter  and  a  correction  is  here  necessary. 

The  details  of  this  method  of  computation  have  been  published  in "j 
an  earlier  bulletin a  of  this  series. 

The  table  summarizing  the  results  of  the  mental  work  tests  follows. 


«  U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  175. 


77 


—  ~  s  —.  i  -  a  a_  - 1 

I  i-H  «      ■  -r  l~  ri  t ri 

a  —  so  cd  -  — 

i  ri  re  ri  M  n  m  ri  ri 


-    Z     -    —  "  ■  =    A  —  A    —  — 


gOCOt-HCtlG   A 

|  id  /:'  m 


y  —  —  i-  ..r  re 


bono  ■-  ^-  tiaa 


«r  re  ri  re  id  re  -r  —  .e  ~  m  re  —  ri  re  in  ri  ri  — ; 
:  re  re  re  re  re  re  fe  H  re  re  re  re 


-    ~'  ',-  /    *  35  3  33  CN  «3  ?  t  -  . 


^  —   .  I  *r  _  _  —  _   .  j  r  -  /   ■;  ;  c  "-  :r;-r  i,/  X  r  1  — . 

!  :e  re  re  r*  re  ri  ri  ri  ri  r-  ri  —  ri  re  ri  ri  r<  re  n 


5Sr 

—   -   : 
s  — 


•  OOdoOAexacOQC  —  —  —  r  ~  —  usee 
'<  '  ~  ' '.  —  i  -  " "  r  -  i  -  .  e  i  -  r  i  r-.  a.  i ^_  -r  —  --  :  i  —  /  j 

~  =  re  -~  —  —  /  r-  t-  ri  -r  re  re  so  us  ~'  i  -  so  rri  ri us  r-  -f 
?£re£— re-r  —  re  —  =  rj  =  re-  i.-r-rr.  —  cri  — 


rr   —  —  -=' 


•—  —      •  ri  T. 


■  r.  ri     >cQO(C 

—  A       ilOON 
SON 


NC4COC  re  r 

rn/rri^r. 


us  oa    ■  i  -  —    •  c  c  -^ 


—  re  X    /.  T  i- 


0 


re  <QNC 

r;  iOOiocC 

:  —  .  —  —;«; 

•  l-  •  — .  i- re 


X  3»Qusysic 

>e  —  t  ri  —  re 

ri  re  ri  —  re  us 
o>  r-  oo  «-  oo  i» 


rr.  -;  r i  —  re  —  . -  —  —  —  —  ~ ~.  ~.-\  <- —  r  -\ 

■  -r  s.  \  -  ~  \  ---'.•--  —  \z  —  nri—  - 

:  — :  i-— '  -r  — '  /  .e  rj  •-'  c  re  /:  re  ri  re  ri  ad  i-  d  so  ■-'  ri 





■*r-  »e  i  -  —  .  ~  —  i  -  -L-i  /- 


.  ■  -   z  -   r    z  -  •  i  -  r  -  -r  A  sg  i_?  —    -  —  i  -  a  --Z-  A  —  A  r  - 

—  _  :  c  -  » c  X rffiOMiotca:  » t-  o  oo  i  — 

:  — '■  -r  —  so  —  re'  ~.  so  r  i  a'  •  -' .  g  -r  ?  i  re  r  i  — '■  r  i  ~ '  — '■  a'  re 

■   ~   T    A    —   -  —  A   —  T.  -    A    T.  -  I  -   —  A   —  ~   ~    ~  —  ~ 


E    '  E 
i-     z- 


-  ~   ~  ~~   _•  ri   _■  -' 

■--  — _  r 


_  —  c  —  c  —  c  —  r_i  o  —  c  —  s  —  c  —  _  — _  r_i 

ci    :  o    ■  z    -o-'    -o    -o    -o    !  e  o  a  p  a  ft 

r:  —  n—  r;—  r^--r:  —  r:  —  r; _-_-,e 

-  . —  . e    .reri-r- ri:.::iri- 

US  O  C  S  OO  O  >C   CSCIOOOtNOOOusOia  —  — 


'   —  —  r<i ; 


-    A    — 


~.~~  :  ~ z. -; r x  .-' >» 


78 

CONTROL  EXPERIMENTS. 

In  order  to  compare  the  metabolism  of  these  subjects  during  the 
mental  work  period  with  a  period  in  which  the  mental  activity  was 
either  at  a  minimum  or,  at  least  presumably,  much  lower  than  that 
during  the  experimental  period  with  mental  work,  each  subject  was 
requested  to  enter  the  calorimeter  for  a  second  or  control  experiment, 
in  which  there  was  little  opportunity  for  mental  work,  though  the 
time  was  occupied.  In  order  to  secure  uniformity  in  movement,  a 
routine. was  followed  in  all  the  experiments.  It  is  believed  that  by 
so  doing  substantially  all  of  the  grosser  muscular  movements  were 
eliminated.  The  minor  movements,  such  as  moving  the  arm  or 
hand,  or  the  involuntary  muscular  movements,  obviously  could  not 
be  the  same  in  both  the  mental  work  and  control  periods.  It  is 
believed,  however,  that  on  the  average  reasonable  uniformity  of 
muscular  activity  in  both  sets  of  experiments  was  secured. 

To  offset  the  muscular  activity  of  writing,  the  total  number  of 
words  written  by  the  subject  on  the  examination  paper  during  the 
mental  work  period  was  counted,  and  he  was  required  to  write  an 
equivalent  number  of  words,  copied  in  part  from  a  formal  report  of 
no  general  interest  and  in  part  from  a  popular  magazine  in  which 
more  interest  would  naturally  be  aroused.  The  copying  from  the 
formal  report  occupied  a  portion  of  the  time  during  the  first  experi- 
mental period  and  the  copying  from  the  magazine  was  done  during 
the  second  experimental  period.  It  was  impossible  under  college 
conditions  to  have  the  control  experiments  follow  immediately  after 
the  mental  work  tests,  but  the  control  tests  were  made  as  soon  as 
possible  after  them. 

Unfortunately,  it  was  inexpedient  to  secure  regularity  in  the 
food  eaten  prior  to  the  control  period,  but  the  control  was  always 
so  arranged  as  to  occur  at  about  the  same  hours  of  the  day  that 
were  covered  by  the  mental  work  test. 

STATISTICS  OF  THE  CONTROL  EXPERIMENTS. 

In  the  following  pages  the  data  for  the  control  experiments  are 
recorded.  In  addition  to  their  value  for  comparison  with  the  mental 
work  tests  these  experiments  throw  interesting  light  on  the  normal 
metabolism  of  healthy  young  men  at  rest. 

CONTROL  EXPERIMENT  No.  23. 

The  experiment  was  made  with  J.  A.  R.  on  the  forenoon  of  Feb- 
ruary 28,  1905.  Breakfast,  which  was  eaten  shortly  before  the 
experiment  began,  consisted  of  2 h  tablespoonfuls  of  cereal  breakfast 
food  with  milk  and  sugar,  and  a  small  slice  of  graham  bread  and 
butter. 


70 


The  subject  staled  thai  he  was  rather  uncomfortable  owing  to  a 
cold,  and  he  states  that  the  period  in  the  respiration  chamber  was 
rather  tedious. 

The  pulse  rate  as  recorded  was  as  follows:  8.25  a.  m.  86,  10.35 
a.  in.  77,  10.37  a.  m.  75,  10.41  a.  m.  82,  12  noon  65,  12.02  p.  m.  68, 
and  12.14  p.  m.  70. 

The  body  temperature  at  the  beginning  of  the  experimental 
period,  9.15  a.  m.,  was  <)S.4°  F.,  and  at  the  end,  12.15  p.  m.,  it  was 
•7.8°  F. 

The  body- weight  at  S.05  a.  m.  was  59.018  kilograms  and  at  12.23 
p.  m.  58.85  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  23. 


Time. 


vapo- 
i  ized. 


9.1")  to  10.45  a.  m 

10.4".  a.  m.  to  12.  15  p.  i;i. 


Grams. 
48.57 
42.45 


Total  for  3  hours. 


Carbon 

dioxid       Oxygen 

climi-     absorbed. 

nated. 


Grams. 

44.1)7 
40.44 


84.51 


Heai 

elimi- 
nated. 


Loss  in 
body 

weight. 


Grams. 
32. 20 
30.00 


62.20 


Calories. 
154.36 
L32.98 


Kilogram. 


287.34 


CONTROL  EXPERIMENT  No.  24. 

This  experiment  was  made  with  II.  ]).  A.  on  the  afternoon  of  Feb- 
ruary 28,  1905.  Dinner,  which  was  eaten  shortly  before  the  experi- 
ment, consisted  of  a  portion  of  potpie  equivalent  to  a  slice  of  beef 
and  2  slices  of  bread,  a  small  potato,  a  portion  of  stewed  tomatoes, 
and  an  orange  of  medium  size. 

According  to  the  subject's  notes,  he  found  the  air  in  the  respira- 
tion chamber  rather  chilly.  The  material  was  easy  to  copy,  the 
report  being  more  interesting  than  the  other  article.  The  copy  was 
pushed  at  4  p.  m. 

The  pulse  rate  taken  at  intervals  was  as  follows:  2  p.  m.  82,  2.30 
|  m.  73,  3  p.  in.  71.  3.32  p.  m.  69,4.  p.  m.  65,  4.30  p.  m.  67,4.58  p.  m. 
f><>.  5.28  p.  in.  63,  and  6  p.  in.  67. 

The  body  temperature  at  2.03  p.  in.  was  98.5°  F.  and  at  5.03  p.  m. 

m°  v. 

The  body  weight  at  I .2  1  p.  in.  was  (>7.2.'!7  kilograms  and  al  5.13 
[>.  m.  65.01  kilogram  . 


1    .... .             .             ...         „ . 

(Jarbon  dioxid,  water  vapor,  and  heat  eliminated  and 

oxygt  a  ' 

bsorbed, 

tperim* 

al  No.   ' i . 

Water 

i 

elimi- 
nated. 

■ 

Heal 
elimi- 
nated. 

body 

2.03  to:;.:;;  |..  n 

11L99 

Kilogram 

9S  31 

80 


CONTROL  EXPERIMENT  No.  25. 

This  experiment  was  made  with  H.  G.  on  the  forenoon  of  February 
24,  1905.  Breakfast  eaten  before  the  experiment  began  consisted  of  a 
shredded-wheat  biscuit,  a  glass  of  milk,  a  tablespoonful  of  sugar,  a 
biscuit,  and  a  cup  of  coffee. 

According  to  the  subject's  notes,  the  air  in  the  respiration  chamber 
seemed  very  warm  for  a  time  and  he  was  drowsy.  He  found  the 
copying  very  easy,  but  in  general  it  was  not  interesting.  The  copy 
was  finished  at  11.28  a.  m. 

The  pulse  rate  as  recorded  was  as  follows:  8.07  a.  m.  71,  8.40  a.  m. 
72,  9.15  a.  m.  69,  9.45  a.  m.  66,  10.15  a.  m.  73,  10.45  a.  m.  71,  11.15 
a.  m.  62,  and  11.50  a.  m.  69. 

The  body  temperature  at  9.15  a.  m.  was  98.1°  F.  and  at  12.15  p.  m. 
98.2°  F. 

The  body  weight  at  8.02  a.  m.  was  49.212  kilograms  and  at  12.23 
p.  m.  49.053  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  25. 


vapo- 
rized. 


Carbon 
dioxid 
elimi- 
nated. 


Oxygen 
absorbed. 


Heat 
elimi- 
nated. 


Loss  in 

body 

weight. 


9.15  to  10.45  a.  m 

10.45  a.  m.  to  12.15  p.  m 

Total  for  3  hours. 


Grams. 
43.15 
45.88 


Grams. 
45.09 
38.52 


Grams. 


Calories. 
116.  47 
116.13 


Kilogram. 


89.  03 


232. 60 


0.110 


CONTROL  EXPERIMENT  No.  26. 

This  experiment  was  made  with  F.  N.  C.  on  the  afternoon  of  Febru- 
ary 25,  1905.  The  dinner  the  subject  ate  shortly  before  the  experi- 
ment began  consisted  of  a  little  potato  and  corned  beef,  some  corn 
fritters,  and  a  piece  of  jelly  cake. 

According  to  the  subject's  notes,  he  found  the  respiration  chamber 
comfortable  and  the  air  good.  He  felt  drowsy  part  of  the  time  and 
the  copying  became  monotonous,  his  hand  and  arm  being  tired. 

The  pulse  rate  as  recorded  was  as  follows:  2.03  p.  m.  72,  2.30  p.  m. 
72,  3  p.  m.  64,  3.30  p.  m.  70,  4.15  p.  m.  70,  4.30  p.  m.  62,  and  4.55 
p.  m.  64. 

The  body  temperature  at  2  p.  m.  was  97.8°  F.  and  at  5  p.  m. 
97.5°  F. 

The  body  weight  at  1.20  p.  m.  was  57.462  kilograms  and  at  5.10 
p.  m.  57.316  kilograms. 


81 


Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  26. 


2  to  3.30  p.  in . 
3.30  to  op.  m. 


Water 
vapo- 
rize 1. 


Grams. 
48.60 
47.  65 


Carbon 

dioxiii       Oxygen 

elimi-      absorbed. 

nated. 


Heat 
elimi- 
nated. 


Grams.      Grams. 
■is.  27  42. 67 

48.84 


Total  for  3  hours 


96.25 


( ulories. 

1 58.  1 7 
L47.22 


Loss  in 

body 

weight. 


Kilogram. 


305.  39 


CONTROL  EXPERIMENT  No.  27. 

This  experiment  was  made  with  J.  V.  C.  on  the  forenoon  of  March 
21,  1905.  Breakfast  before  the  experiment  began  consisted  of  3 
pancakes  with  butter  and  sirup  and  a  cup  of  coffee  with,  sugar  and 
milk. 

According  to  the  subject's  notes,  he  drank,  shortly  after  the  ex- 
periment began,  106  cubic  centimeters  water  and  passed  380  cubic 
centimeters  urine.  He  felt  perfectly  comfortable  during  the  entire 
experimental  period,  but  found  the  report  which  he  copied  rather 
tedious.     The  copy  was  finished  at  11.40  a.  m. 

The  pulse  rate  as  recorded  was  as  follows:  8.33  a.  m.  74,  8.55  a.  m. 
71.  9.25  a.  m.  75,  9.55  a.  m.  67,  10.25  a.  m.  66,  10.55  a.  m.  60,  11.25 
a.  m.  65,  and  11.40  a.  m.  65. 

The  body  temperature  at  8.48  a.  m.  was  98°  F.  and  at  11.48  a.  m. 
97.9°  F. 

The  body  weight  at  8.01  a.  m.  was  63.144  kilograms  and  at  11.57 
62.946  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  /.'. 


Time. 

Water 

rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 

Ileal              LOSS  in 

elimi-           body 
nated.          weight. 

Grams. 
66.  86 

Gill  UK. 

Grams. 

\j  :;s 

( 'alories.     Kilogram. 
165.17 

63.  24          11-  82 

31.62 

1 54.  52    

130. 10 

74.00 

CONTROL  EXPERIMENT  No.   28. 

This  experiment  was  made  with  A.  M.  on  the  afternoon  of  March  1, 
1905.  Dinner,  which  was  euten  shortly  before  the  experiment  began, 
consisted  of  a  plate  of  soup,  a  plate  of  baked  beans,  with  fried  potatoes, 
4  slices  of  toast,  a  glass  of  milk,  ;i  cup  of  tea.  and  an  apple. 

According  to  the  subject's  notes,  he  was  perfectl)  comfortable  in 
the  respiration  chamber,  though  sleepy  In  the  early  part  of  the  ex- 
perimental period,  lie  found  the  copying  not  at  all  tedious,  though 
076     B   II   208    09        6 


82 


it  was  done  rather  mechanically,  his  mind  being  on  something  else 
while  engaged  with  it. 

The  pulse  rate  as  recorded  was  as  follows:  2  p.  m.  81,  2.45  p.  m. 
76,  3.30  p.  m.  73,  and  4.15  p.  m.  70. 

The  body  temperature  at  1.48  p.  m.  was  98.8°  F.  and  at  4.48  p.  m. 
98.3°  F. 

The  body  weight  at  1.14  p.  m.  was  66.638  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  28. 


Water 
vapo- 
rized. 


Carbon 
dioxid 
elimi- 
nated. 


Oxygen 
absorbed. 


Heat 
elimi- 
nated. 


Loss  in 

body 

weight. 


1.48  to  3.18  p.  m 

3.18  to  4.48  p.  m 

Total  for  3  hours 


Grams. 
53.59 
59.37 


Grams.  I  Grams. 
51.50  I  40.69 
53.64  41.35 


Calories. 
160. 24 
151. 53 


Kilogram. 


105. 14 


82.04 


311.77 


0.145 


CONTROL  EXPERIMENT  No.  29. 

This  experiment  was  made  with  F.  E.  R.  on  the  forenoon  of 
February  25,  1905.  Breakfast  taken  before  the  experiment  began 
consisted  of  a  small  dish  of  oatmeal  with  milk  and  sugar  and  a  cup 
of  coffee  with  milk  and  sugar. 

The  subject  stated  in  his  notes  that  during  the  early  'part  of  the 
experimental  period  he  felt  decidedly  warm  and  that  in  general  the 
copying  was  uninteresting  and  tiresome.  He  finished  writing  at 
11.20  a.  m. 

The  pulse  rate  as  recorded  was  as  follows:  8.12  a.  m.  99,  9.20  a.  m. 
94,  9.39  a.  m.  97,  10.02  a.  m.  86,  10.35  a.  m.  82,  11  a.  m.  88,  11.23 
a.  m.  88,  and  12.03  p.  m.  90. 

The  body  temperature  at  9  a.  m.  was  99.3°  F.  and  at  12  noon 
99.2°  F. 

The  body  weight  at  8.02  a.  m.  was  52.981  kilograms  and  at  12.09 
p.  m.  52.747  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  29. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 

elimi- 
nated. 

Loss  in 

body 

weight. 

9  to  10.30  a.m 

Grams. 
68.16 
56.37 

Grams. 
43.64 
42.09 

Grams. 
34.42 
30.65 

Calories. 
163.  65 
137.  59 

Kilogram. 

10.30  a.  m   to  12  noon 

Total  for  3  hours 

124.53 

85.73 

65.07 

301. 24 

0.170 

83 


CONTROL  EXPERIMENT  No.  30. 

This  experiment  was  made  with  J.  W.  H.  on  the  afternoon  of 
March  23,  1905.  Lunch,  which  was  eaten  shortly  before  the  experi- 
ment began,  consisted  of  2  glasses  of  milk,  2  slices  of  bread  and  but- 
ter. 4  slices  of  cold  corned  beef  with  horseradish,  a  sugar  cooky,  and 
a  piece  of  cocoanut  cake. 

In  general  the  subject  states  that  he  felt  much  the  same  as  in  the 
mental  work  experiment  (see  p.  67),  but  found  the  copying  rather 
dull  and  monotonous. 

The  pulse  rate  as  recorded  was  as  follows:  1.50  p.  m.  71,  2.35 
p.  m.  69,  3.30  p.  m.  70,  and  4.30  p.  m.  69. 

The  body  temperature  at  1.40  p.  m.  was  98.5°  F.  and  at  4.40 
p.  m.  98.3°  F. 

The  body  weight  at  1.05  p.  m.  was  61.26  kilograms  and  at  4.40 
p.  m.  61 .063  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  SO. 


Time. 

Wat  or 
vapo- 
rized. 

Car!  >on 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 

elimi- 
nated. 

Loss  in 
body 

weight. 

1.40  to  3.10  p.  in 

Grams. 
69.15 
73.34 

Grams.    1    Grams. 
61.88  '        51.92 
58. 51           45. 21 

Calories. 

170.42 
174.  75 

Kilogram. 

3.10  to  4.40  p.  in 

Total  for  3  hours 

142.49 

120.39           97.  IS 

345. 17 

0. 1G5 

CONTROL  EXPERIMENT  No.  31. 

This  experiment  wras  made  with  C.  A.  R.  on  the  forenoon  of  March 
L8,  1905.  The  breakfast  which  the  subject  ate  before  the  experi- 
ment consisted  of  2  dishes  of  oatmeal,  a  glass  of  milk,  and  some  fried 
potato*-. 

According  to  the  subject  "s  notes,  be  found  the  copying  monotonous, 
t  bough  the  magazine  was  more  interesting  than  the  report,  ;ind  he 
found  it  difficult  to  keep  from  being  interested  in  it. 

The  pulse  rate  as  recorded  was  as  follows:  '.)  a.  m.  108,  9.30  a.  m. 
100,  10  a.  m.  95,  10.30  ;i.  m.  87,  II  a.  m.  89,  11.30  a.  m.  77,  12  noon 
7s.  and  12.30  p.  m.  85. 

The  body  temperature  ;it  8.57  a.  m.  was  98.3'  F.  mid  at  11  Ju  a.  m. 
98°  V 

The  body  weight  .-it  8.16  a.  m.  was  59.73  kilograms  and  at  12.08 

p.  m.  59.5  1  1  kilograms. 


84 


Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  31. 


Time. 


Water 
vapo- 
rized. 


Carbon 
dioxid 
elimi- 
nated. 


Oxygen 
absorbed, 


Heat 
elimi- 
nated. 


Loss  in 

body 

weight. 


8.57  to  10.27  a.  m 

10.27  to  11.57  a.  m 

Total  for  3  hours 


Grams. 
60.03 
58.45 


Grams. 
55.05 
46.93 


Grams. 
41.94 
36.18 


Calories. 
160. 91 
141.  53 


Kilogram. 


118.  48 


101.  98 


302.  44 


0.144 


CONTROL  EXPERIMENT  No.  32. 

This  experiment  was  made  with  G.  H.  H.  on  the  forenoon  of  March 
23, 1905.  Breakfast,  eaten  before  the  experiment  began,  consisted  of 
a  saucer  of  dry  cereal  with  sugar  and  milk,  2  biscuits,  and  a  glass  of 
milk. 

The  subject  states  that  he  did  not  feel  fatigued  during  the  experi- 
mental period.  In  his  opinion  the  copying  required  some  mental 
work,  and  he  felt  that  mere  scribbling  would  have  been  more  nearly 
equivalent  to  the  mechanical  effort  of  the  mental  work  experiment 
(see  p.  68). 

The  pulse  rate  as  recorded  was  as  follows:  9.05  a.  m.  97,  9.34 
a.  m.  90,  10.09  a.  m.  88,  10.45  a.  m.  85,  11.15  a.  m.  91,  and  11.45 
a.  m.  85. 

The  body  temperature  at  8.47  a.  m.  was  98.5°  F.  and  at  11.56 
a.  m.  98.6°  F. 

The  body  weight  at  8.23  a.  m.  was  51.656  kilograms  and  at  12.37 
p.  m.  51.484  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  32. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 
elimi- 
nated. 

Loss  in 

body 

weight. 

8  47  to  9.56  am                                      

Grams. 
42.  44 
72.91 

Grams. 
39.45 
59.99 

Grams. 
31.11 
59.10 

Calories. 
103. 86 
176.  02 

Kilogram. 

115.  35 

99.44 

90.21 

279.  88 

0.125 

CONTROL  EXPERIMENT  No.  33. 

This  experiment  was  made  with  H.  L.  W.  on  the  afternoon  of 
February  24,  1905.  Dinner,  eaten  before  the  experiment  began,  con- 
sisted of  a  small  portion  of  roast  beef,  a  small  potato  with  gravy,  a 
small  dish  of  green  peas,  a  biscuit,  a  portion  of  bread  pudding,  and 
a  glass  of  milk. 

According  to  the  subject's  notes,  he  began  writing  at  2.24  p.  m. 
and  at  4.04  had  finished  ten  pages.     This  he  reviewed  and  then 


85 

wrote  two  pages  additional.  He  found  the  lighl  rather  troublesome. 
He  was  somewhat  sleepy  during  the  experimental  period,  as  he  had 
slept  only  eight  hours  during  the  preceding  sixty  hours.  He  found 
that  copying  the  magazine  article  required  less  effort  than  copying 
the  report. 

The  pulse  rate  as  recorded  was  as  follows:  2.05  p.  m.  86,  2.30 
p.  m.  SO,  3  p.  m.  SO,  3.35  p.  m.  74,  4  p.  m.  6S,  4.35  p.  m.  69,  and 
5.05  p.  m.  69. 

The  body  temperature  at  2.22  p.  m.  was  99°  F.  and  at  5.22  p.  m. 
9S.30  F. 

The  body  weight  at  1.20  p.  m.  was  51.623  kilograms  and  at  5.32 
p.  m.  51.419  kilograms 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  33. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 
elimi- 
nated. 

Loss  in 
body 
weight. 

2.22  to  3.52  p.  m 

Grams. 
00.42 
60.58 

Grams. 
48.92 
40.59 

Grams. 
40.45 
33.84 

Calories. 
155.  19 
148.58 

Kilogram. 

121. 00 

89.51 

74.29 

303.  77 

0. 146 

CONTROL  EXPERIMENT  No.  34. 

This  experiment  was  made  with  D.  R.  F.  on  the  forenoon  of  March 
2,  1905.  The  subject  had  eaten  for  breakfast  oatmeal  with  milk, 
soda  crackers,  a  hot  biscuit,  and  an  apple. 

According  to  his  notes,  he  found  the  light  satisfactory  and  was  in 
no  way  inconvenienced  by  Ids  stay  in  the  respiration  chamber.  The 
materia]  copied  was  not  very  interesting  and  no  appreciable  differ- 
ence was  noted  in  this  respect  between  the  report  and  the  magazine 
article. 

The  pulse  rate  as  recorded  was  as  follows:  S.24  a.  m.  83,  9  a.  m. 
87,  9.45  a.  m.  80,  10.15  a.  m.  72,  11  a.  in.  70,  and  1 1.30  a.  m.  68. 

The  body  temperature  at  8.46  a.  m.  was  98°  F.  and  at  11.46  a.  m. 
97.7°  V. 

The  body  weight  at  8.14  a.  in.  was  62.583  kilograms  and  at  11.55 
a.  in.  62.429  kilograms. 

Carbon  dioxid,  mi i, i-  vapor,  and  heat  eliminated  and  oxygen  nl>x<>rin</,  experiment  X<>.  -:i. 


i  hue. 

Water 

\  :||IM- 

rized. 

dioxid 

ellml 

nated. 

II. Ml 

e 

uated. 

Loss  in 

body 

weight. 

10  16  to  1  I  46  a  in                                   

ii  i. 

4a  :('J 

144.89 

Kilogram. 

91.08 

104.80 

279.  I'' 

o  126 

86 


CONTROL  EXPERIMENT  No.  35. 


This  experiment  was  made  with  J.  N.  T.  on  the  afternoon  of  March 
2,  1905.  The  subject  had  eaten  for  dinner  shortly  before  the  experi- 
ment a  pork  chop,  2  boiled  potatoes,  a  dish  of  cooked  onions,  2  slices 
of  bread,  and  a  piece  of  prune  pie. 

According  to  the  subject's  notes,  he  had  a  slight  headache  for  part 
of  the  period  and  thought  that  the  air  in  the  respiration  chamber 
was  somewhat  closer  than  in  the  mental  work  experiment  (see  p.  70). 
He  found  the  copying  uninteresting. 

The  pulse  as  taken  at  intervals  was  as  follows:  1.45  p.  m.  78,  2.30 
p.  m.  93,  3.30  p.  m.  73,  4.30  p.  m.  63,  and  5  p.  m.  61. 

The  body  temperature  at  2.16  p.  m.  was  98.7°  F.  and  at  5.16  p.  m. 
97.7°  F. 

The  body  weight  at  1^)7  p.  m.  was  63.596  kilograms  and  at  5.25 
p.  m.  63.406  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  35. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 
elimi- 
nated. 

Loss  in 

body 

weight. 

2.16  to  3.46  p.  m 

Grams. 
49.14 

56.77 

Grams. 
56.02 
52.66 

Grams. 
41.76 
41.11 

Calories. 
180.  69 
164.  68 

Kilogram. 

3.46  to  5.16  p.  m 

105.  91 

108. 68 

82.87 

345.  37 

0.132 

CONTROL  EXPERIMENT  No.  36. 

This  experiment  was  made  with  H.  C.  A.  on  the  forenoon  of 
February  27,  1905.  Breakfast,  which  was  eaten  shortly  before  the 
experiment  began,  consisted  of  a  cup  of  coffee  with  sugar  and  milk, 
one-half  glass  of  milk,  3  or  4  crackers,  and  6  graham  biscuits  with 
butter. 

According  to  the  subject's  notes,  he  was  not  especially  sleepy  during 
the  experimental  period  and  was  somewhat  interested  in  the  report 
and  the  magazine  article  which  he  copied,  but  more  particularly  in 
the  latter. 

The  pulse  rate  as  recorded  at  intervals  was  as  follows:  9  a.  m.  69, 
9.51  a.  m.  58,  10.28  a.  m.  54,  10.58  a.  m.  54,  and  11.36  a.  m.  48. 

The  body  temperature  at  8.52  a.  m.  was  97.8°  F.  and  at  11.52  a.  m. 
97.3°  F. 

The  body  weight  at  8.10  a.  m.  was  59.019  kilograms  and  at  12.01 
p.  m.  58.883  kilograms. 


87 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  36. 


Time. 


S.52  to  10.22  a.  m 

10.22  to  11.52  a.  m 

Total  for  3  hours 


Water 
vapo- 
rized. 


Grams. 
42. 80 
39.66 


82.46 


Carbon 

dioxid 
elimi- 
nated. 


(hams-. 
48.  55 
43.04 


91.59 


i  >xygen 
absorbed 


Grams. 
36.79 

35.  SS 


TIeat, 
elimina- 
ted. 


Calories. 

162.  41 
135. 80 


298.21 


Loss  in 

body 

weight. 


Kilogram. 


CONTROL  EXPERIMENT  No.  37. 

This  experiment  \v;is  made  with  F.  C.  B.  on  the  afternoon  of  March 
22,  1905.  Dinner  eaten  not  long  before  the  experiment  began  con- 
sisted of  2  slices  of  roast  beef,  2  small  potatoes,  a  small  dish  of  string 
beans,  a  small  piece  of  lemon  pie,  an  orange,  and  a  cup  of  coffee  with 
milk. 

The  subject  states  in  his  notes  that  he  found  the  light  good  and  was 
comfortable,  the  air  in  the  respiration  chamber  being  warm  at  first 
and  cold  later  on.  He  preferred  the  copying  to  the  mental  work  of 
the  earlier  experiment  of  which  he  was  the  subject.     (See  p.  71). 

The  pulse  rate  as  recorded  was  as  follows:  1.55  p.  m.  88,  2.25  p.  m. 
87,  3.10  p.  m.  81,  3.55  p.  m.  79,  4.55  p.  in.  77,  5.40  p.  m.  76,  and  6.05 
p.  m.  74. 

The  body  temperature  at  2.21  p.  m.  was  98.5°  F.  and  at  6.09  p.m. 
97.8°  F. 

The  body  weight  at  1.20  p.  m.  was  74.728  kilograms  and  at  6.17 
]).  in.  74.45  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  37. 


Time. 


2.21  to  3.51  p.  m 

3. 51  to  6.09  [..in 

Total  for  3  hours  and  4.H  mimiles 


Water 
vapo- 
rized. 


Grams. 
69.  i-i 
112.89 


182. 03 


Carbon 
dioxid 
elimi- 
nated. 


(I in  ins. 
56.50 
7(i.  87 


L33.37 


Oxygen 
absorbed 


<;  i,i  ins. 

in. (is 
86.08 


106.70 


lle;i! 

elimina- 
ted. 


( 'dim  us. 

L86.82 
249.  so 


136. 71 


Loss  in 

body 

weight. 


Kilogram. 


0.214 


CONTROL  EXPERIMENT  No.  38. 

Thia  experiment  was  made  with  (1.  E.  II.  on  the  forenoon  of  March 
22, '1905.  The  subject  had  eaten  for  breakfast  a  dish  of  rolled  oats 
u ith  milk  and  a  muffin. 

In  his  not.-  thr  subject  states  thni  he  felt  sleepy  during  the  experi- 
mental period,  particularly  while  copying  the  report.  When  working 
with  tin-  magazine  he  found   it   somewhat  difficult  to  refrain  from 


reading  the  various  articles,  but  did  not  do  any  extended  or  connected 
reading. 

The  pulse  rate  as  recorded  was  as  follows:  9.10  a.  m.  61 ,  10  a.  m. 
58,  10.30  a.  m.  60,  11.30  a.  m.  56,  and  11.56  a.  m.  60. 

The  body  temperature  at  9.07  a.  m.  was  97.5°  F.  and  at  12.07  p.  m. 
97.4°  F. 

The  body  weight  at  8.03  a.  m.  was  63.146  kilograms  and  at  12.18 
p.  m.  62.994  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  38. 


Water 
vapo- 
rized. 


Carbon 
dioxid 
elimi- 
nated. 


Oxygen 
absorbed. 


ITeat 
elimina- 
ted. 


Loss  in 

body 

weight. 


9.07  to  10.37  a.  m 

10.37  a.  m.  to  12.07  p.  m 

Total  for  3  hours. 


Grams. 
53.14 
50.39 


Grams. 
41.49 
36.77 


Grams. 
32.01 
29.81 


Calories. 
132. 89 
119. 68 


Kilogram. 


78.26 


61.82 


252.  57 


0.107 


CONTROL  EXPERIMENT  No.  39. 

This  experiment  was  made  with  N.  M.  P.  on  the  afternoon  of 
February  27,  1905.  Lunch  eaten  a  short  time  before  the  experiment 
began  consisted  of  4  chicken  sandwiches,  2  cups  of  cocoa,  and  an 
orange. 

In  Ins  notes  the  subject  states  that  he  found  the  cop}dng  tiresome 
and  became  sleepy.     He  required  about  five  minutes  to  write  a  page. 

The  pulse  rate  as  recorded  was  as  follows:  1.58  p.  m.  73,  2.35  p.  m. 
73,  3.15  p.  m.  64,  3.38  p.  m.  62,  4.57  p.  m.  59,  and  5.55  p.  m.  56. 

The  body  temperature  at  2  p.  m.  was  98.7°  F.  and  at  5  p.  m. 
98.4°  F. 

The  body  weight  at  2  p.  m.  was  69.805  kilograms  and  at  5.10  p.  m. 
69.668  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  39. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 
elimi- 
nated. 

2to3.30p.m 

Grams. 
50.86 
56.76 

Grams. 
54.02 
58.56 

Grams. 
43.85 
46.28 

Calories. 
180  04 

3.30  to5p.  m 

174  83 

Total  for  3  hours 

107.  62 

112.  58 

90.13 

354  87 

CONTROL  EXPERIMENT  No.  40. 


This  experiment  was  made  with  G.  W.  S.  on  the  forenoon  of 
March  25,  1905.  Breakfast  eaten  before  the  experiment  began 
consisted  of  2  dishes  of  oatmeal  and  3  muffins. 


89 


The  subject  states  that  he  felt  indolent  throughout  the  whole 
experimental  period,  and  took  a  longer  time  to  write  the  1'.)',  pages, 
which  he  completed,  than  he  did  for  the  examination  with  which  he 
was  engaged  in  the  earlier  experiment  (see  p.  73). 

The  pulse  rate  as  recorded  was  as  follows:  8.50  a.  m.  93,  9.15  a.  m. 
88,  9.45  a,  m.  93,  10.15  a,  m.  81,  10.45  a.  m.  79,  11.15  a,  m.  79, 
11.4.3  a.  m.  80,  12  noon  79,  and  12.30  p.  m.  71. 

The  body  temperature  at  9.10  a.  m.  was  97.4°  F.  and  at  12.10 
p.  m.  97.6°  F. 

The  body  weight  at  8.09  a.  m.  was  50.771  kilograms  and  at  12.19 
p.  m.  50.651  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  40. 


Time. 

Water 
vapo- 
rized. 

Carbon 
dioxid 
elimi- 
nated. 

Oxygen 
absorbed. 

Heat 

elimi- 
nated. 

Loss  in 

body 

weight. 

9.10  to  10.40  a.  m 

Grams. 
57.22 
56.34 

Grams. 
42.73 
40.02 

Grams. 
38.94 
26.  93 

Calories. 
124.88 

125.  39 

Kilogram. 

10.40  a.  in.  to  12.10  p.  m 

Total  for  3  hours 

113.56 

82.75 

65.87 

250.  27 

0.087 

CONTROL  EXPERIMENT  No.  41. 

This  experiment  was  made  with  A.  G.  on  the  afternoon  of  March  18, 
1905.  Dinner,  which  was  eaten  before  the  experiment,  consisted  of 
roast  pork  with  potatoes,  3  slices  of  bread  and  butter,  a  piece  of 
lemon  pie,  and  a  dish  of  prunes. 

Jn  his  notes  the  subject  states  that  he  felt  warm  in  the  earl}7  part 
of  the  experimental  period  and  that  the  time  passed  very  slowly. 
He  was  rather  more  interested  in  the  magazine  article  than  in  the 
report  which  he  copied. 

The  pulse  rate  as  recorded  was  as  follows:  2.04  p.  m.  92,  2.30 
p.  in.  84,  3.07  p.  m.  84,  3.20  p.  m.  72,  3.50  p.  m.  72,  4.30  p.  m.  66, 
and  4.55  p.  in.  70. 

The  body  temperature  at  2  p.  m.  was  97.9°  F.  and  at  5  p.  m. 
97.7°  F. 

The  body  weigh!  at  1.12  p.  m.  was  63.313  kilograms  and  at  5.11 
p.  in.  63. 102  kilograms. 


Carbon  dim  id,  water  vapor,  mid  heat  eliminated  and 

oxygen  absorbed, 

experiment  No.  41. 

Time. 

Wilier 
v:if><>- 

rlzed. 

r|io\ic| 

elimi- 

nated 

Oxygen 

II.  Ml 

elimi- 
nated. 

body 

i  p.  in 

6a  27 
81.87 

ii  .'ii 

I7:(.  (Hi 

Kilogram 



42.  59 

1  Hi.  14 

86.79 

n  [59 

90 


CONTROL  EXPERIMENT  No.  42. 


This  experiment  was  made  with  H.  L.  K.  on  the  forenoon  of 
March  1,  1905.  The  subject  had  eaten  for  breakfast  that  morning  a 
banana,  4  tablespoonfuls  of  dry  cereal  with  15  teaspoonfuls  of  cream, 
a  cup  of  coffee  with  10  teaspoonfuls  of  cream,  and  2  teaspoonfuls  of 
sugar,  an  egg,  a  biscuit,  and  a  doughnut,  or  practically  the  same 
breakfast  as  in  the  earlier  experiment  of  which  he  was  the  subject 
(see  p.  74). 

In  his  notes  he  states  that  he  was  not  at  all  excited,  though  he 
had  a  slight  headache.  He  found  it  somewhat  difficult  not  to 
become  interested  in  the  report  which  he  copied.  The  copying  was 
completed  at  11.35  and  he  then  spent  twenty  minutes  in  glancing 
over  what  he  had  written. 

The  pulse  rate  as  recorded  was  as  follows:  8.15  a.  m.  95,  8.28 
a.  m.  90,  8.35  a.  m.  93,  8.45  a.  m.  97,  8.57  a.  m.  91,  9.20  a.  m.  82, 
9.35  a.  m.  84,  9.50  a.  m.  71,  10.15  a.  m.  72,  10.45  a.  m.  75,  11.15 
a.  m.  70,  and  11.45  a.  m.  76. 

The  body  temperature  at  8.54  a.  m.  was  98.1°  F.  and  at  11.54 
a.  m.  98.5°  F. 

The  body  weight  at  8  a.  m,  was  57.165  kilograms  and  at  12.04 
p.  m.  57.019  kilograms. 

Carbon  dioxid,  water  vapor,  and  heat  eliminated  and  oxygen  absorbed,  experiment  No.  42., 


Time. 


Water 
vapo- 
rized. 


Carbon 
dioxid 
elimi- 
nated. 


Oxygen 
absorbed. 


Heat 
elimi- 
nated. 


Loss  in 
body- 
weight. 


8.54  to  10.24  a.  m 

10.24  to  11.54  a.  m 

Total  for  3  hours 


Grams. 
48.85 
43.85 


Grams. 
45.47 
42.28 


Grams. 
37.31 
34.50 


Calories. 
143. 84 
128. 04 


Kilogram. 


87.75 


0.108 


CONTROL  EXPERIMENT  No.  43. 

This  experiment  was  made  with  G.  G.  R.  on  the  forenoon  of  March 
20,  1905.  Breakfast  that  morning  consisted  of  2  dishes  of  a  cooked 
wheat  breakfast  food  with  milk,  milk  toast,  and  coffee. 

The  subject  states  that  he  found  the  experimental  period  some- 
what tedious  and  the  report  which  he  copied  uninteresting.  The 
magazine  article  was  a  little  more  interesting.  The  temperature  of 
the  respiration  chamber  was  satisfactory. 

The  pulse  rate  as  taken  at  intervals  was  as  follows:  9  a.  m.  76, 
9.45  a.  m.  70,  10.30  a.  m.  70,  11.15  a.  m.  68,  and  12  noon  69. 

The  body  temperature  at  8.53  a.  m.  was  98.6°  F.  and  at  11.53  a.  m. 
98.5°  F. 

The  body  weight  at  8.01  a.  m.  was  77.272  kilograms  and  at  12.06 
p.  m.  77.03  kilograms. 


91 


Carbon  dioxid,  water  vapor,  and  hurt  eliminated  andoxygen  absorbed,  experiment  No.  4$. 


'rime. 

Water 
rized. 

dioxid 
elimi- 
nated. 

( ixygen 
absorbed. 

Heal 
elimi  - 
nated. 

Loss  in 
body 

10.23  a.  m 

Grams. 
66.  45 

(ill.  18 

Grams. 

61.  H 
55.03 

Grams. 

Calories. 
L75.33 

L64  l"i 

Kilogram. 

10.23  to  11.53  a.  m 



Total  for  3  hours 

132. 03 

116.14 

339.  48 

' 

CONTROL,  EXPERIMENT  No.   44. 

This  experiment  was  made  with  E.  M.  S.  on  the  afternoon  of  March 
21,  1905.  The  subject  ate  no  dinner  with  the  exception  of  about 
one-fourth  of  an  orange,  but  had  eaten  for  breakfast  about  five  hours 
before  the  experiment  began  a  banana,  a  portion  of  dry  cereal  with 
3  tea-spoonfuls  of  sugar  and  one-fourth  pint  of  cream,  a  few  raisins, 
a  fig,  about  one-half  pint  of  milk,  and  a  slice  of  whole-wheat 
bread  with  5  or  6  grams  of  peanut  butter. 

According  to  the  subject's  notes,  the  air  in  the  respiration  chamber 
was  rather  warm  at  first,  though  later  on  it  became  rather  cool.  Copy- 
ing the  magazine  article  he  considered  more  interesting  than  the 
report.  Toward  the  end  of  the  experimental  period  he  states  that 
he  was  rather  hungry. 

The  pulse  rate  as  recorded  at  intervals  was  as  follows:  2.30  p.  in. 
80,  2.50  p.  m.  78,  3.20  p.  m.  74,  3.43  p.  m.  72,  4.14  p.  m.  7fi,  1.50  p.  m. 
7."..  and  5.12  p.  m.  74. 

The  body  temperature  at  2.1(5  p.  ni.  was  !)S.4°  F.  and  at  5.1(1  p.  in. 
98.2°  F.  ' 

The  body  weight  at  1.33  )).  in.  was  64.446  kilograms  and  at  5.26 
j).  in.  04.272  kilograms. 

Carbon  <li<ni<l,  water  vapor,  mnl  heat  eliminated  and  oxygen  absorbed,  experiment  No.  i'i. 


2.16  to  :;  1'.  p  in 

8.46  to  6.16  p.  in 


Water 
rized. 


124.29 


Carbon 
elimi-     absorbed. 


Grams.      C 

-.1  48.59 

60  15 


annus. 
40.21 
32.  i  u 


elimi- 
nated. 


I    llllllll  s 

ITS.  16 
[50  -II 


Loss  in 
body 


Kilogram. 


0.  13fi 


SUMMARY   OF  RESULTS  OF  CONTROL  EXPERIMENTS. 


The  carbon  dioxid  mid  water  eliminated,  the  oxygen  consumption, 
and  til*-  heat  production  in  the  control  experiments  are  summarized 
in  t la-  following  table. 


92 


fldfi  o> 


.1—1  f- 

tfWH©iot»OOGriOCOCOOJMH 

-* 

ficod 

5 

CONWX'-M  CC  Cc  cc  lo  CO -rr  CO  »o  t^  to 
(NMNCTM^:  Ol  O)  C)  01  Ol  CI  0-J  C)  CI  CI 

<N 
<N 

.  O  CC  iO  N  N  00  O  O  (N  00  O  N  l- .^.  c  C  C  ■ ":  'M  '7i  <M  X 
to'^COQOOOONO^Oi^'il'OcOCO'OcDCOcDOWOiO 

ti  co  co  co  co  co  co  cj  co  co  cc  --  cc  cc  cc  re  co  co  co  co  co  co  <N 


^CNMhOMOcONOIONI/jNC  -0   ~  X  CI  CO  <o  lO 
;  Oi  Ol  CO  iO  GO  CO  'O  O  CI  O  ^  VI  CO  0 ■')  C>  r-  CO  CO  00  O  C  ' 


.  ci  r- 1  co  io  o  co  co  cr.  oo  >o  o  oo  ^h  co  co  co  ci  co  ci  rr  co  ~ 

iOOlONHQiO^liMOOa'^CiOC'iOOOMOIN 


p  ~. ;  CO  X  ~-  CO  —  C  J  ~*  ' 


-  »-  CI  CI  CO  I  -  CO  O  CI  (M  -^r 

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~  ~  ~  c~.  ~  x  x  ~  ~  ~  ~  ~.  ~  ~  cr.  X' 


CO  TT  iC  O!  O  rH  O  t-  O  CO  I-  C)  O  H  N  W 


H  N  io  N  rf  co  ei  -+  Z  O  -*1  CO'  CO  CO  O  O 
lO  IO  Tf  C  "  CO  '-0,  LQ  O  ^  N  -^  O  "^  C"C 


O  -^  N  CO  N  rH  ffl  N  N  N  C  CN  CO  N  O  H 

OOOhhc)ci:17.  O  t-X-iCON  x 


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Jco^WQdcoco'r-«r-id'ico»occ;t^  ci  r-1  ci  cd  -^  ai  cd 


;HCSHrHCO^C0ac0TtirHCC0'C:NO00»0TJ,i0'*C0 
G-J4O05C©'— i  CO  i— INCOOJ^iOWtO  lOCOC-UOb-Hh-HiO 

STf^coVNiood-Hcid^cttTHcoaicNwdNcrirH 
e  oo  i— i  cc  cr.  c  c  co-  ci  c  —  x  o  co  c~.  co  i -  •—«  oo  »-h  oo  i— i  oi 


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p. 

ci  "CJ 


o  »o 


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J  O  •  ^O  Or-'OOOOOOOOc  M  ;  M0  O  O 
C3+^>  Coio-»^+J   pj-^+^-f^-^+J+i-^'+J  C3  O  C3  UO  +^»  +^  -^ 

m  co  m  o  oo  oo  .ONNncococinNoootinco 
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93 


DISCUSSION    OF   RESULTS    OF    MENTAL    WORK    AND    CONTROL 

EXPERIMENTS. 

In  discussing  the  mental  work  experiments  and  the  control  tests 
it  seems  besl  to  consider  specifically  the  pulse  rate,  the  body  temper- 
ature, the  carbon  dioxid  and  water  outgo,  the  heat  production,  and 
the  oxygen  consumption  of  the  subject  in  the  two  periods  rather  than 
to  attempt  on  the  basis  of  the  available  experimental  data  a  discus- 
sion of  general  metabolism. 

BODY  TEMPERATURE. 

The  body  temperature  at  the  beginning  and  end  of  the  experi- 
mental period  in  both  the  mental  work  and  control  experiments  and 

the  average  temperature  at  the  beginning  and  end  of  each  experi- 
ment are  recorded  in  the  table  below.  It  will  be  remembered  that 
these  temperatures  were  taken  in  the  mouth,  the  thermometer  being 
inserted  by  the  subject  himself,  ami  although  it  was  retained  in  the 
mouth  for  five  minutes  and  all  precautions  were  taken  to  secure  as 
satisfactory  a  temperature  measurement  as  possible,  nevertheless  it 
is  only  with  the  average  results  that  any  satisfactory  comparison 
can  be  made. 

Comparison  of  body  temperature,  mental  nod-  and  control  <  tperiments. 


— 

Mental 
work  ex- 
periments. 

Control  ex- 
periments. 

-    . 

8| 

a 

V 

Mental 
work  ex- 
periments. 

Control  ex- 
periments. 

-i  \ 

x-9 

—  5 

Subject. 

m  0 

■—   ~Z 
0   - 

81 

_  3 

Subject. 

z  z 

5 

ti. 

B 

S 

a 

z  ~ 

"a 

3  fl 

a 

■z  = 

E 

a 

j     i 

X) 

I1 

— 

.5 

•6 

■| 

-r 

; 

~ 

0            v 

a 

o 

V                 ~ 

a 

* 

= 

H         pq 

- 

~ 

•_ 

-       - 

- 

w 

0  F. 

°  F. 

°  F. 

°F. 

°F. 

°F. 

°F. 

23 

J. 

A.  R 

98.  -:. 

97  -:.     9&  4 

13 

35 

J. 

X.  T 

99.  i 

98.  8 

98.7 

07.7 

24 

II 

D.  A 

98.7 

98.  5 

H 

il 

C  A 

os.  9 

07.  9 

07.  S 

07.  3 

II 
F 

Q 

99.0 

98.  1 

98.  2     98.  1 

'.<7.  8     97.  8 

os.  2 
07.  5 

15 

in 

37 

F. 
Q 

C  B 

E.  II 

99.  2 

OS.    1 

98  9 

os.  3 

OS.  ;, 
07.  5 

07. 'S 

X.  C 

07.  1 

.'7 

J. 

V.  c 

98.  3 

M.S.  II 

'17.0 

17 

39 

X 

\1.   P 

OS.  0 

98.  ."■ 

OS.  7 

'.is.  1 

A 

M..  jr 

99  2 

98.  (i 

98.  3 

18 

in 

w.  s...\... 

os.  6 

os,  8 

07.  1 

97.6 

1  . 
.1. 

E.  Ii 

W.  II 

99.  I     99.3 

99.  2 

'is.  3 

10 
-0 

11 
42 

A. 
II 

Q 

os.  6 
98.  o 

os.  2 
os.  9 

07.0 
OS.  1 

07.  7 

I..  K 

31 

1  . 

A.  l: 

99.2 

!is.  0 

.'I 

13 

'. 

<;.  i; 

99.  3 

OS.  0 

9a  5 

ID 

32 

a 

II.  11 

22 

II 

E 

M.    

os. ;, 

OS.   1 

1  ] 

ii 

I     w 

07.7 

» 

\'i.  I ■■.".'.'.'.'.'. 

Avei 

98.9 

OS.    1 

98.3 

OS.  II 

a  \..i  Included  in  I 

The  results  recorded  above  show  that  the  average  sublingual  tem- 
poral lire  of  t  he  men  jusl  before  beginning  t  he  examinai  ion  was  (.)S.<)°  I<\ 
Ai  the  end  of  the  three-hour  examination  period  the  averagetem- 
perature  l    F.,  or  a  fall  of  0.5°.     [n  the  case  of  the  control  period 

the  average  initial  temperature  was  98.3°  F.,  or  0.6°  lower  than  the 
for  the  mental  work  test.  In  spite  of  the  fad  thai  the  ini- 
tial temperature  was  somowhal  lower  than  the  initial  temperature 
of  the  mental  work  test  there  \\;i>  likewise  ;i  fall  in  temperature 
during  the  control  period,  the  final  temperature  I »« ■  i 1 1 _r  98    F.     Thi 


94 

corresponds  to  a  fall  of  0.3°.  The  data  also  show  that  the  body 
temperature  was  on  the  whole  slightly  higher  during  the  mental 
work  experiments  than  during  the  control,  and  that  the  fall  in  tem- 
perature during  the  three-hour  period  was  slightly  greater  during 
the  mental  work  than  during  the  control  experiment.  To  interpret 
these  facts  it  is  necessary  to  take  into  consideration  the  pulse  rate. 

PULSE  RATE. 

The  method  of  obtaining  the  pulse  rate  in  these  experiments  is 
open  to  the  objection  that  the  subjects  recorded  their  own  pulse 
rates.  To  free  the  observations  from  as  much  error  as  possible,  they 
were  carefully  instructed  how  to  count  the  pulse,  and  to  simplify 
the  counting  they  were  told  to  count  a  certain  number  of  beats  and 
register  the  time  on  a  stop  watch,  a  method  which  it  is  believed  would 
make  for  accuracy.  However,  many  of  these  subjects  had  never 
counted  their  own  pulse,  and  it  is  fair  to  assume  that  there  were  some 
unavoidable  errors  in  the  observations. 

The  average  pulse  rates  during  both  the  mental  and  control  periods 
are  tabulated  below. 

Average  pulse  rates. 


Pulse  rate. 

Pulse  rate. 

Mental 
work 

Control 
experi- 

Mental 
work 

Control 
experi- 

ment 

ment 
num- 

Subject. 

Mental 
work 

Control 

experi- 
ment 

ment 
num- 

Subject. 

Mental 

Control 

num- 
ber. 

ber. 

experi- 
ments. 

ments. 

number. 
13 

ber. 

experi- 
ments. 

experi- 
ments. 

1 

23 

J.  A.R 

80 

73 

35 

J.N.'T 

78 

73 

2 

24 

H.  D.  A 

72 

09 

14 

36 

H.C.  A 

61 

57 

3 

25 

H.  G 

73 

68 

15 

37 

F.C.  B 

82 

79 

4 

26 

F.N.C 

68 

68 

16 

38 

G.  E.H 

70 

59 

5 

27 

J.  V.C 

70 

67 

17 

39 

N.M.  P 

63 

65 

6 

28 

a.  M.,  jr 

78 

75 

18 

40 

G.  W.S 

83 

83 

7 

29 
30 

F.  E.  R 

J.  W.  II 

89 
83 

89 
70 

19 
20 

41 
42 

A.  G 

81 
96 

77 

8 

H.  L.  K 

78 

9 

31 

C.  A.  R 

76 

93 

21 

43 

G.  G.R 

83 

71 

10 

32 

G.  II.  II 

117 

89 

22 

44 

E.M.  S 

89 

76 

33 

34 

79 
69 

73 

75 

12 

D.R.  F 

Average... 

79 

74 

The  average  values  for  all  the  experiments  show  that  the  pulse 
rate  was  79  during  the  mental  work  experiments  as  against  74  dur- 
ing the  control,  and  that  in  only  three  instances  was  the  pulse,  rate 
higher  in  the  control  than  in  the  mental  work  tests.  An  examina- 
tion of  the  individual  experiments  shows  wide  fluctuations.  Thus 
the  subject  of  experiment  No.  10  showed  an  average  pulse  rate  of 
117  during  the  examination  period  compared  with  89  during  the 
control,  while,  on  the  other"  hand,  the  subject  of  experiment  No.  9 
showed  an  average  pulse  rate  of  but  76  during  the  mental  test,  as 
against  93  during  the  control. 

One  possible  explanation  of  the  slightly  higher  average  pulse  rate 
observed  during  the  mental  work  tests  is  that  these  .subjects  had 
had  no  experience  inside  the  respiration  chamber  prior  to  the  mental 
work  experiments,  and  so  were  nervous.     Although  each  man  entered 


95 


the  chamber  an  hour  before  the  experiment  proper  began,  the  pulse 
rate  was  doubtless  increased  as  the  result  of  the  novelty  of  the  situ- 
ation. The  personal  impressions  of  the  men  show  that  they  were 
all  very  much  more  calm  at  the  end  of  the  experiment  than  when 
they  first  entered  the  calorimeter. 

It  is  not  inconceivable,  and.  indeed,  it  is  highly  probable,  that  the 
body  temperature  was  likewise  somewhat  affected  by  the  slight  excite- 
ment attending  the  first  experience  in  the  respiration  chamber. 
This  is,  however,  far  from  denying  that  there  may  have  been  suffi- 
cient excitement  attending  the  expectation  of  the  examination  to 
account  for  the  difference  both  in  body  temperature  and  pulse  rate. 
Obviously,  if  the  effect  of  the  novelty  of  the  situation  is  not  con- 
sidered, it  is  necessary  to  assume  that  the  increased  body  tempera- 
ture and  pulse  rate  were  results  of  the  mental  activity  incident  to 
the  taking  of  a  college  examination. 

WATER  VAPOR  EXCRETED. 

Water  may  leave  the  lungs  and  skin  as  water  vapor,  or,  in  the  case 
of  sensible  perspiration,  may  leave  the  skin  in  the  liquid  form,  ll 
i>  a  common  popular  impression  that  mental  work  frequently  pre- 
disposes to  profuse  sensible  perspiration,  and,  indeed,  a  number  of 
subjects  of  these  experiments  were  inclined  to  the  belief  that  the 
severe  mental  work  of  examination  made  them  perspire.  In  this 
connection  a  comparison  of  the  total  water  vapor  output  is  of  espe- 
cial interest.  The  comparison  is  made  in  the  table  following,  which 
shows  not  only  the  total  weights  of  water  vapor  eliminated,  but  also 
the  water  per  kilogram  of  body  weight  per  hour: 

Comparison  of  the  amounts  of  water  vapor  eliminated  during  mental  work  mid  control 

experiments. 


work 
experi- 
menl 

7)11111- 

ber. 

Control 
experi- 
ment 
num- 
ber. 

Subject. 

Total  weigh!  of 
water  eliminated. 

Water  eliminated 

per  hour. 

Water  eliminated 

per  kilogram  body 

weight  per  hour. 

Menial 

work 

I'.vfH-ri- 

experi- 
ment . 

Menial 
work 

lllelll. 

Control 
experi- 

Mental 

work 

experi- 
ment. 

Control 
experi- 
ment . 

i 
_• 

a 

23 
24 

■j.:, 

i: 
:n> 
33 

.1.  A.  K 

II.  1).  A 

II.  '■ 

(! Ill  III: 

100. 56 
133.60 

106.  12 

111.78 
131.29 
148.76 
119.58 
137.59 
112.  7H 
10420 

103.84 
[36.71 

'i.-,  ii 
170.  S7 
'17   61 

112.26 

in;,  i- 

1 1 1  -  ; 

'.ii  ii.' 
130.91 
89.03 

■Hi   ■:, 

Kill.  Ml 

iil'. '.in 
124.63 
142.  19 

1 1 :..  ■■',:, 
121.00 

91.08 
In:,.  !H 

82  46 
182.03 
103.53 
107.62 
ii;;  56 

Grams. 
33.  52 

44.  50 
35.  :i7 

H7.20 

49  69 

45.  B6 

33.08 
ll  30 
34.61 

HI.  70 

II  'i, 

16  i- 
33  ll 

<!  III  III:. 

30.34 
43.  64 
29.68 
32.  OS 

:i7.  65 
41.51 

36.62 

47.90 

::i  :,i 
36.  87 

13  '.i 

it  .'i 
ii    13 

o.  57 
.68 

.72 
.64 
.69 

.74 
.77 
.70 
.  66 
i.i 
.so 
.  56 

1 

.61 
.  66 
,64 

ni 

.01 

60 

dm  in. 

.00 

4 

r, 

7 
K 

F.  N.  C 

.r.  v.  c  

A.  M.jr 

J.  W.  II... 

.  .",1 , 

.69 

.      .  7,7 

.7!) 

'< 

C.  A    H 

.00 

10 

<;.  ii.  ii  . .     . 

.71 

11 

li.l.  \v 

.78 

12 

is 

14 

:t7 

1.    i:    I 

.  to 
i. 

I.', 

I    '      B 

i.i 

16 

<.    1.    I! 

.  66 

17 

4<l 
41 

a 

ii 

•    P 

i.    \\     - 

.M 
.7.r> 

10 

\  <; 
ii    i.   K 

i.'i 
■  1 

21 

i: 

.1 

'•J 

96  . 

From  the  data  it  is  seen  that  on  the  average  there  were  119.55 
grams  of  water  vapor  eliminated  during  the  mental  work  experiments 
and  115.4  grams  during  the  control  experiments.  It  thus  appears 
that  the  mental  work  experiments  caused  an  increase  of  4.15  grams 
in  the  water  vapor  leaving  the  body.  While  this  is  an  appreciable 
difference,  it  is  certainly  much  less  than  would  be  expected.  It  is 
important  to  note  that  in  the  individual  experiments  wide  differ- 
ences in  the  amounts  of  water  vapor  eliminated  during  the  two 
periods  of  experiments  may  be  found.  Thus,  36  grains  more  water 
were  eliminated  by  the  subject  of  experiments  Nos.  6  and  28  during 
the  mental  work  than  during  the  control  experiment,  while  with 
the  subject  of  experiments  Nos.  19  and  41,  on  the  other  hand,  18  grams 
more  were  eliminated  during  the  control  than  during  the  mental.  On 
the  average  it  would  appear  that  the  mental  effort  resulted  in  an 
increased  elimination  of  water  vapor  amounting  to  3.7  per  cent. 
Inasmuch,  however,  as  45  per  cent  of  the  subjects  eliminated  more 
water  in  the  control  tests  than  in  the  mental  work,  the  apparent 
value  of  this  deduction  is  greatly  lessened. 

The  marked  differences  in  the  individual  experiments  disappear  to 
a  slight  extent  when  the  water  per  kilogram  of  body  weight  per  hour 
is  computed,  although  the  average  water  vapor  elimination  per 
kilogram  of  body  weight  per  hour  is  somewhat  larger  during  the 
mental  work  experiments  than  during  the  control. 

The  determinations  of  carbon  dioxid  and  oxygen  consumption  and 
the  nitrogenous  products  of  the  urine  during  mental  work  and  control 
periods  have  been  studied  by  other  investigators.  We  believe  that 
the  experiments  here  reported  represent  the  first  instance  where  the 
water-vapor  output  has  been  accurately  studied  in  any  systematic 
manner  in  tests  where  sustained  mental  effort  is  one  of  the  conditions 
of  the  experiment.  In  the  report  of  the  earlier  experiments  made  in 
this  laboratory  on  the  effects  of  mental  work  a  the  determination  of 
water  vapor,  while  attempted,  was  extremely  unsatisfactory,  and 
indeed  was  not  of  sufficient  accuracy  to  warrant  publication. 

CARBON  DIOXID  EXCRETED. 

As  an  easily  determined  and  reasonably  approximate  index  of 
changes  in  metabolism  the  carbon  dioxid  elimination  during  the 
mental  work  and  the  control  experiments  is  of  interest.  The  com- 
parison is  made  in  the  following  table. 

"U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  44. 


97 

Coinparison  of  the  amounts  of  carbon  dioxid  eliminated  during  mental  work  and  control 

,  I 1 1,  riim  nts. 


Mental 

Control 
experi- 
ment 

Total  carbon 

dioxkl  elimi- 

Carbon  dioxid 
eliminated  per 

Carbon  dioxid 
eliminated  per 
kilogram  of  body 

Carbon  dioxid 

eliminated  per 

kilogram  of  body 

work 

weigh!  per  hour. 

weight  per  minute. 

experi- 

Subject. 

ment 

Dum- 
ber. 

num- 
ber. 

Mental 
work 

Control 

Mental 
work 

Control 

"88?  Coutrol 

Mental 

Control 

experi- 
ment. 

experi- 
ment. 

experi- 
ment. 

experi- 
ment. 

experi- 
ment. 

experi- 
ment. 

work  ex- 
periment . 

experi- 
ment. 

Grams. 

Grams. 

Grams. 

Gra  ms. 

Gram. 

Gram. 

Cc. 

Cc. 

l 

23 

J.A.R 

101  13 

84.51 

33.  71 

28  17 

0.57 

0.48 

4.83 

4.06 

o 

24 

H.D.  A 

94  00 

111.99 

31.33 

37.33 

.48 

.56 

4.08 

4.72 

3 

25 

H.G 

81.94 

83.61 

27.31 

27.  s7 

.  56 

.57 

4.71 

4.  S2 

4 

26 

F.N.C 

106  09 

97.  11 

35.36 

32.37 

.61 

.  56 

5.19 

4.79 

5 

27 

J.V.C 

101.60 

97.  63 

33  87 

32.  54 

.54 

.  52 

4.55 

4.38 

6 

28 

A.M..jr 

113  94 

105. 14 

37.  98 

35.05 

.57 

.53 

4.80 

4.47 

7 

29 

F.E.R 

89  1)7 

85.73 

29  69 

28.58 

.58 

.54 

4.89 

4.59 

8 

30 

T.W.H 

116  s7 

120. 39 

38.  96 

40.13 

.64 

.66 

5.46 

5  57 

9 

31 

C.A.K 

92  14 

101.98 

30  71 

33.99 

.53 

.57 

4.48 

4.84 

10 

32 

G.  II.  U 

'.is  4s 

99.44 

31.26 

31.57 

.61 

.61 

5.15 

5  19 

11 

33 

II.  L.W 

85  66 

89.51 

28  55 

29.  84 

.  55 

58 

4.  67 

4  92 

12 

34 

D.R.F 

95  07 

104.80 

31.69 

34.  93 

.51 

.  56 

4.  32 

4.74 

13 

35 

J.  N.T 

124  21 

ins  r,,s 

41.40 

36  23 

.  66 

.57 

5.61 

4.84 

14 

36 

nc  a 

102  56 

91.59 

34  19 

30  53 

.58 

.52 

4.94 

4.40 

15 

37 

F.C.  B 

143  61 

133  37 

37.  79 

35  10 

.52 

.47 

4.42 

3  99 

16 

38 

C..E.II 

82.67 

78.26 

27.  56 

26  09 

.44 

.41 

3.70 

3.51 

17 

39 

N.  M.  P 

114  ss 

112.58 

38  29 

37.53 

.55 

.54 

4.64 

4.57 

18 

40 

G.W.S 

92.  76 

82.  75 

30  92 

27.58 

.59 

.54 

5.03 

4.62 

IS 

41 

A.G 

100  08 

110.14 

33  36 

36  71 

.54 

.58 

4. 62 

4.93 

20 

42 

H.  L.  K 

91.81 

s7.  7.-. 

30  60 

29. 25 

.54 

.51 

4.  55 

4.35 

21 

43 

G.  G.  R 

108  7s 

116   14 

36  26 

38  71 

.46 

.50 

3  93 

4.26 

22 

44 

E.M.S 

Average. . 

103  17 

91  58 

34.39 

30  53 

.54 

.47 

4.55 

4.03 

101. 84 

99.76 

33.42 

32. 76 

.55 

.54 

4.69 

4.57 

While  there  are  large  differences  between  the  two  sets  of  experi- 
ments when  individuals  are  considered,  the  average  results  show  that 
101.84  grams  of  carbon  dioxid  were  excreted  during  the  mental  work 
experiments,  while  during  the  control  experiments  90.76  grams  were 
excreted.  It  thus  appears  that  during  the  mental  work  experiments 
about  2  per  cent  more  carbon  dioxid  was  excreted  than  during  the 
control  experiments.  For  purposes  of  comparison  the  carbon  dioxid 
per  hour  per  kilogram  of  body  weight  per  hour  and  the  volume  per 
kilogram  of  bodyweighl  per  minute  are  likewise  given, and  show  also 
the  same  variations  as  have  been  noted. 


OXYGEN  ABSORBED. 

The  direct  determination  of  the  amounts  of  oxygen  absorbed  was 
attempted  in  ;ill  the  experiments,  but  the  results  were  unsatisfactory 
in  eight  of  the  twenty-two  experiments,  owing  to  the  fad  thai  it  was 
necessary  to  make  the  experiments  in  quick  succession,  and  under  I  he 
circumstances  less  attention  could  be  given  to  this  factor  than  would 
otherwise  be  the  case. 

70076— Bull.  208—09 7 


98 

The  results  obtained  for  the  oxygen  consumption  are  given  in  the 
table  which  follows : 

Comparison  of  the  amounts  of  oxygen  absorbed  during  mental  work  and  control  experi- 
ments. 


Mental 

work 

experi- 

Control 
experi- 
ment 
num- 
ber. 

Subject. 

Total  oxygen 
absorbed. 

Oxygen  ab- 
sorbed per  hour. 

Oxygen  ab- 
sorbed per  kilo- 
gram of  body 
weight  per  hour. 

Oxygen   absorbed 

per  kilogram  of 

body  weight  per 

minute. 

ment 
num- 
ber. 

Mental 
work 
experi- 
ment. 

Control 
experi- 
ment. 

Mental 
work 
experi- 
ment. 

Control 
experi- 
ment. 

Mental 
work 
experi- 
ment. 

Control 
experi- 
ment. 

Mental 
work  ex- 
periment . 

Control 
experi- 
ment. 

1 
2 

23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
33 
34 
35 
36 
37 
38 
39 
40 
41 
42 
43 
44 

J.A.R 

H.D.  A 

H.  G     

Grams. 
77.04 

Grams. 
62.20 
99.30 

Grams. 
25.68 

Grams. 
20.73 
33.10 

Gram. 
0.43 

Gram 

0.35 

.49 

Cc. 
5.06 

Cc. 
4.11 
5.75 

3 

4 
5 
6 

F.N.C 

J.V.C.. 

A.M.,jr 

F.E.R 

J.  W.  H 

C.  A.R 

77.08 
88.40 

"'76.22' 
96.70 

74.00 
82.04 
65.07 
97.13 
78.12 
90.21 
74.29 
78.27 
82.87 
72.67 
106.  76 
61.82 
90.13 
65.87 
86.79 
71.81 

72.88 

25.69 
29.47 

23.41 
32.23 

24.75 
23.54 

31.60 
24.86 
35.44 

30.86 
24  40 
27.47 
23.42 
27.68 
25.12 

24.67 
27.35 
21.69 
32.38 
26.04 
28.64 
24.76 
26.09 
27.62 
24.22 
28.10 
20.61 
30.04 
21.96 
28.93 
23.94 

24.29 

.44 
.47. 

.45 
.53 

.48 
.45 

.50 
.42 
.49 
.29 
.44 
.47 
.45 
.41 
.35 
.39 

.39 
.41 
.41 
.53 
.44 
.56 
.48 
.42 
.44 
.41 
.38 
.33 
.43 
.43 
.43 
.42 

.38 

5.18 
5.44 

4.57 
4.80 

7 
8 
9 

5.30 
6.21 

4.79 
6.18 
5.10 

10 
11 
12 

G.H.H 

H.L.W 

D.R.F 

J.N.T 

H.C.A 

F.C.  B 

G.E.H 

77.95 
70.63 

"94."80" 
74.57 
134.  66 

5.60 
5.29 

6.48 
5.61 
4.87 

'     13 
14 
15 
16 

5.89 
4.94 
5.70 

5.08 
4.79 
4.82 
3.81 

17 
18 
19 
20 
21 

N.M.  P 

G.W.S 

A.G 

H.L.K 

G.G.R 

E.M.S 

Average. . 

92.58 
73.19 
82.40 
70.25 
83.05 
75.35 

5.15 
5.46 
5.23 
4.79 
4.12 
4.57 

5.03 
5.05 
5.34 

4.89 

22 

4.40 

84.20 

79.48 

27. 30 

25.86 

.46 

.43 

5.33 

5.08 

In  the  average  values  presented  in  the  above  table,  only  those 
experiments  in  which  the  oxygen  consumption  was  determined  during 
both  periods  are  included.  The  results  show  that  on  the  average  84.2 
grams  of  oxygen  was  absorbed  during  the  mental  work  period  and 
79.48  grams  during  the  control  period,  a  difference  much  greater  than 
has  been  observed  with  any  of  the  other  factors  thus  far  considered. 
The  oxygen  consumption  by  weight  per  kilogram  of  body  weight  per 
hour  and  the  volume  per  kilogram  of  body  weight  per  minute  are 
likewise  recorded  in  the  table  and  emphasize  the  facts  already  pointed 
out.  While  the  difference  between  the  mental  work  and  control 
experiments  here  indicates  an  increased  metabolism  during  the 
mental  work  experiment  of  over  6  per  cent,  two  facts  must  not  be  lost 
sight  of  in  considering  these  results;  first,  that  the  figures  above  are 
the  averages  of  14  rather  than  22  experiments,  and  second,  that  it  has 
repeatedly  been  demonstrated  in  this  laboratory  that  the  determina- 
tion of  oxygen  for  short  periods,  especially  when  the  periods  are  not 
consecutive,  is  extremely  unsatisfactory  as  a  basis  for  comparison. 
It  would  be  manifestly  unwise,  therefore,  to  draw  definite  conclusions 
from  the  data  for  oxygen.  The  data  available,  however,  in  our 
opinion  indicate  that  on  an  average  there  was  a  slightly  increased 
metabolism  during  the  mental  work  period. 


99 


HEAT  PRODUCTION. 


The  table  which  follows  summarizes  the  data,  showing  the  amounts 
of  heat  produced  during  the  mental  work  and  the  control  experiments: 

Comparison  of  the  amounts  of  hail  "produced during  mental  work  and  control  experiments. 


Mental 
work 

«xperi- 
ment 
num- 
ber. 


Control 
experi- 
ment 
num- 
ber. 


Subject. 


23  J.  A.  R 

24  H.  D.  A 

25  H.  G 

26  F.  X.  C 

27  J.  V.  C... 

28  A.  M..  jr 

29  F.  E.  R 

30  J.  W.H 

31  C.  A.  R 

32  G.  II.  II 

33  II.  L.  W 

34  D.  R.  F 

35  J.  X.  T 

36  II.  C.  A 

37  F.  C.  B 

38  G.  E.  II 

39  X.  M.  P 

40  G.  W.  S 

41  A.  G 

42  II.  L.  K 

43  G.  G.  R 

44  E.  M.  S 

Average 


Total  heat  pro- 
duced. 


Mental  Control 
work  ex-  experi- 
periment.     ment. 


Calories. 


266. 

327. 
247. 
300. 
307. 
347. 
268. 
326. 
275. 


267. 
361. 
264. 
429. 
260. 
349. 
273. 
281. 
283. 
329. 
298. 


Calories. 
269. 15 
322.  97 
233.22 
295.  41 
318. 36 
293. 83 
295. 59 
340.06 
292.07 
280.29 
284.60 
268.27 
313.  68 
282.  77 
409. 66 
247. 66 
343. 19 
253.48 
318. 12 
280.43 
332.  55 
320.  45 


301.13         299.81 

I 


Heat  produced  per 
Heat  produced  per  kilogram  of 

hour.  body  weight 

per  hour. 


Mental  Control  ;  Mental 
work  ex-  experi-  work  ex- 
periment,    ment.     periment. 


Calories. 
88.72 

109. 27 
82.34 

100.21 

102.40 

115.68 
89.46 

108. 80 
91.94 
91.57 
89.88 
89.14 

120.  40 
88.33 

112.89 
86.93 

116.  56 
91.07 
93. 90 
94.  52 

109.  95 
99.61 


Calories. 
89.72 

107.66 
77.74 
98.47 

106.12 
97.94 
98.53 

113.35 
97.36 
88.98 
94.87 
89.42 

104.56 
94.26 

107. 81 
82.55 

114.40 
84.49 

106.  04 
93.48 

110.85 

106.82 


98. 80 


98.43 


Calories. 
1.50 
1.68 
1.67 
1.73 
1.62 
1.72 
1.74 
1.80 
1.58 
1.78 
1.73 
1.43 
1.92 
1.50 
1.56 
1.37 
1.67 
1.75 
1.53 
1.66 
1.40 
1.55 


Control 
experi- 
ment. 


Calories. 
1.52 
1.60 
1.58 
1.72 
1.68 
1.47 
1.86 
1.85 
1.63 
1.73 
1.84 
1.43 
1.65 
1.60 
1.45 
1.31 
1.64 
1.67 
1.68 
1.64 
1.44 
1.66 


1.63 


1.62 


Since  the  respiration  calorimeter  offers  a  means  of  determining  with 
very  ^reat  accuracy  the  heat  elimination  of  man,  it  is  probably  true 
that  with  the  aid  of  these  measurements  the  heat  production  can, 
under  favorable  conditions,  be  computed  with  great  accuracy.  The 
sources  of  error  in  the  computations  of  the  heat  production  in  these 
particular  experiments  have  been  touched  upon  in  the  discussion  of 
body  temperature.  (See  p.  93.)  It  is  believed,  however,  thai 
notwithstanding  these  minor  errors  the  measurements  of  heat  pro- 
duction as  recorded  in  the  table  above  are  as  satisfactory  as  could 
be  expected.  The  results  show  marked  differences  in  the  heat  pro- 
duction during  mental  work  and  control  experiments  with  certain  of 
tlie  subjects.     Bui  considering  all  the  data  and  comparing  average 

figures,  the  total  heat  production  during  the  mental  work  experiments 

was  on  the  average  301.13  calories,  while  during  the  control  experi- 
ments it  was  299.8  calories,  or  about  one-half  of  I  per  cent  less  in  the 
Control  than  in  the  mental  work  tests. 

The  values  for  heal  production  per  hour  and  per  kilogram  of  body 
weight  per  hour  are  likewise  included  in  the  table.  Obviously,  the 
same  percentage  differences  appear  in  these  values  as  in  those  for 

total   heal    production.       A-  a   result  ,  then,  of  the  measurement   of  heat 


100 

production  of  twenty-two  individuals  during  a  mental  work  and 
control  experiment  the  average  results  show  that  the  heat  production 
during  the  mental  work  period  was  about  one-half  of  1  per  cent 
greater  than  during  the  control  period,  a  veiy  small  amount  and  one 
which  seems  well  within  the  limits  of  error  due  to  small  differences  in 
the  amount  of  muscular  work  in  the  two  periods,  and  to  other  unavoid- 
able variations  in  the  experimental  conditions. 

GENEKAL  CONCLUSIONS. 

From  the  results  of  the  data  accumulated  in  this  series  of  experi- 
ments on  the  effects  of  mental  work  on  metabolism  it  would  appear 
that  the  pulse  rate  was  slightly  increased,  the  body  temperature 
somewhat  higher,  the  water  vapor  output  increased  by  about  5  per 
cent,  the"carbon  dioxid  production  increased  by  about  2  per  cent,  the 
oxygen  consumption  increased  by  about  6  per  cent,  and  the  heat 
production  increased  by  about  one-half  of  1  per  cent  as  a  result  of 
sustained  mental  effort  such  as  obtains  during  a  college  examination. 
Of  these  factors,  those  most  accurately  measured  are  undoubtedly  the 
carbon  dioxid  elimination  and  the  heat  production.  On  the  whole, 
however,  the  increase  of  both  of  these  factors  accompanying  the 
mental  exertion  is  so  small  and  the  exceptions  are  so  numerous  that 
it  would  not  be  wise  to  say  whether  or  not  the  mental  activity  exer- 
cised a  positive  influence  on  metabolic  processes  in  general.  Indeed, 
more  than  half  of  the  subjects  studied  produced  more  heat  in  the  con- 
trol than  in  the  mental  work  test,  which  might  be  considered  as  nega- 
tive evidence.  This  is  especially  so  when  it  is  considered  that  although 
every  precaution  was  taken  to  eliminate  all  other  extraneous  influences 
it  still  remains  a  fact  that,  with  many  of  these  subjects,  the  experi- 
ments during  the  mental  work  period  was  their  first  experience  inside 
of  a  complicated  respiration  chamber  and  they  were  more  or  less  dis- 
turbed by  the  novel  experience,  and  perhaps  more  restless — that  is, 
made  more  muscular  movements  than  during  the  control  period.  I 
view  of  this  fact,  we  are  very  strongly  of  the  opinion  that  the  results 
obtained  in  these  experiments  do  not  indicate  that  mental  effort  has  a 
positive  influence  on  metabolic  activity. 

O 


COLUMBIA  UNIVERSITY 

This  book  is  due  on  the  date  indicated  below,  or  at  the 
expiration  of  a  definite  period  after  the  date  of  borrowing, 
as  provided  by  the  rules  of  the  Library  or  by  special  ar- 
rangement with  the  Librarian  in  charge. 

DATE  BORROWED 

DATE  DUE 

DATE  BORROWED 

DATE  DUE 

DEC  1  - 1 

W 

C23!638)M50 

QP171  B43 

Eenedict 
Influence  of  muscular  and  mental 
work  on  metabolism 


1  fc  1947      £ 


DEC  1  fc 1947 


